Add the docs for triggers v0.20.0

Add most recent release `v0.26.x` and `main` as the only options for
now as we've updated the structure and links to ensure they work
correctly on both GitHub and the website.

References to the Katacoda scenarios have been removed
from the docs and website so we should also remove the content now.

Update the dev section as recommended by `netlify dev` to avoid
the framework selection prompt on startup. Without this the command
hangs waiting for user input. See output from netlify CLI that
suggested the change:

```
$ netlify dev
◈ Netlify Dev ◈
◈ Injected netlify.toml file env var: HUGO_VERSION
◈ Ignored general context env var: LANG (defined in process)
◈ Ignored general context env var: LC_ALL (defined in process)
? Multiple possible start commands found Hugo-hugo server -w
Add 'framework = "hugo"' to the [dev] section of your netlify.toml to avoid this selection prompt next time
◈ Starting Netlify Dev with Hugo
hugo server \
        --baseURL http://localhost:8888/ \
        --buildDrafts \
        --buildFuture \
        --disableFastRender \
        --ignoreCache \
        --watch
```

Remove `blackfriday` and use `goldstar` as default parser for hugo.

The blackfriday has been outdated and is giving rendering issues in some [cases](https://github.com/tektoncd/website/issues/323).
As it is also not being maintained, it better to switch to default markdown parser supported and encouraged by [hugo docs](https://gohugo.io/getting-started/configuration-markup/#configure-markup).

Using this the render issue for [interceptors](https://github.com/tektoncd/website/issues/323) was fixed

Include a series of introductory videos that can be very helpful for
many new users.

Add the docs for triggers v0.18.0 & v0.19.0, and updated v0.17.0 to v0.17.1

Closes https://github.com/tektoncd/website/issues/366

- [x] tekton.dev home page
	- [x] Get started with interactive tutorials' which links to https://tekton.dev/try/
		- Update the link text to: 'Get started with Tekton.'
		- Update the URL to point to our new tutorial: `https://tekton.dev/docs/getting-started/`
- [x] 'Try Tekton' block towards the bottom of the page which links to the Katacoda playground scenario
	- Update the text to: 'Learn, explore, and experiment with Tekton by following the tutorial.'
	- Make the word 'tutorial' a link with URL pointing at `https://tekton.dev/docs/getting-started/`
- [x] 'Try' link in the site header which also links to `https://tekton.dev/try/`
	- remove the link, page, and associated content

Since we're removing the 'Try' page from the website, as well as
the associated Katacoda scenarios, remove the reference to this
from the end of the asciinema recording which is displayed on
the home page.

This commit makes some updates to the concepts informations:

- Update the navigation to keep the conceptual information under the
  "Concepts" section, including the main Overview.

- Delete references to deprecated PipelineResources.

- Update path for images to be absolute instead of relative. In some
  documents relative paths don't render correctly.

Updating the website configuration to include the two latest major releases.

Alpine containers don't have bash, so need to change the first line.

Introductory guide for newcomers. This is a two-file quickstart that
shows a simple example to create a task and a pipeline.

These tutorials do not include new information. The information here is
reorganized to be easier to understand for newcomers. Including
prescritpive steps that the user just has to copy/paste .

Currently the netlify deploy uses hugo v0.53, which is almost 4 years
old and has some big inconsistencies when rendering markdown. This bumps
hugo up to the latest release.

The current version of Jinja2 cases issues with the transitive
dependency markupsafe. Updating to a recent version fixes the
issue.
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>

Pipeline v0.33.0 was released today.
Add the docs for the last four versions of pipeline - it was not updated
since v0.29.x.

Using v0.33.x as display name so that we don't need to update the sync
config on minor releases.
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>

Workadound for https://github.com/tektoncd/triggers/issues/1306 until
the fix is merged on triggers side.
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>

Step 1: Restore the previous reference output and adapt the Task YAML to match it

Accordingly add the version tag to the `image` key in the YAML

The version of `pytest` specified in `dev_requirements.txt` is incompatible with Python 3.10. In order to make the Katacoda experience as reproducible as possible, it’s a good practice to use fixed versions for as many things as possible anyway.

Signed-off-by: NVille Aikas <vaikas@chainguard.dev>

Currently only points at main. Tagged released docs will come later.

- Move the contribution guidelines to the documentation folder so they
  show up in the website. Some minor updates were introduced to reflect
  the agreements about documentation strategy.

- Update the roadmap. It now includes the main points agreed about the
  docs strategy going forward.

Thank you Geri for your contributions to the Docs WG!!
The community PR is merged https://github.com/tektoncd/community/pull/562
This one is to keep the OWNERS file in sync.
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>

Add configuration for chain docs.
Front matter is missing so adding some basic one just to test the
PR. The docs include images at least one image (the logo) which
does not work as the only mime type supported for in-repo data is
text / markdown - which is something we need to fix in the sync
script.

This also adds support for using "." to get documents from the
repo root.
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>

Documentation may contain links to local files which are neither
text/markdown nor text/plain. Add support for those file by loading
them as binary (no decoding) and writing them as-is as binary in
the target location.
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>

displayOrder and docDirectory are not used anymore by the sync
script, so remove them from config, docs and tests.

The default target is now "" and not "/" anymore, so fix a few
comments where it referred to the old value.
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>

Release v0.25.x branch has been created on pipeline side to add
documentation updates. Switch the config to the branch so that
we pull in any doc updates.
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>