Docsy now has versioned releases and uses Hugo modules (a wraper around
Go modules), this PR update the website to be compatible with the latest
version of Docsy.

- Create go.mod and go.sum files for compatibility with Hugo modules.
- Delete checked in theme and dependencies.
- Update base layout for compatibility with latest theme.
- Update packaje.json to match required dependencies and replace legacy
  values

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The blackfriday has been outdated and is giving rendering issues in some [cases](https://github.com/tektoncd/website/issues/323).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

Hugo supports markdown emojis in the :<name>: format by they are
disabled by default. Enable them as might be used in Tekton docs.

Fixes #268
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>

Tekton is a cloud native project, not necessarily a kubernetes native
project, and in fact (beyond basing our design around k8s style
resources and using k8s containers) we try to minimize our coupling to
k8s (at least in our API).

If you look at our README you can see that we are k8s-style and cloud
native: https://github.com/tektoncd/pipeline#-tekton-pipelines

You can see this reflected in our mission as well:
"Be the industry-standard, cloud-native CI/CD platform components and
ecosystem."
https://github.com/tektoncd/community/blob/master/roadmap.md#mission-and-vision

This commit updates the wording to be a bit more accurate.

Add support for a custom page param that can be used to point the
links in the sidebar to the correct project repos.

'Edit this page' will open the editor pointing to the correct file
in the project repo, instead of trying to find it in the website repo.

'Create an issue' will open the new issue UI in the target project repo.

Adjusts theme to support CD Foundation's requirements for copyright, privacy, and terms footer.

Adds favicon.ico at root

Fixes #13

Explicitly set the markup engine as blackfriday so the site renders with the current version of hugo.

See https://github.com/google/docsy-example for details.

Signed-off-by: Nlucperkins <lucperkins@gmail.com>