* Add Sneakers link to documentation list.

The advice for symbol/block form is taken from the Active Record guides.

[ci skip]

[ci skip]

The hyphenated form "back-end" only appears once in this guide; elsewhere, the un-hyphenated form "backend" is used consistently.

The immediate runner is no longer default, the async adapter is.

@prathamesh-sonpatki

[ci skip] Added note on child class maintaining parent's queue adapter.

[ci skip] Added note on child class maintaining parent's queue adapter.

[ci skip] removed documentation for child class inheriting the queue adapter.

If you can't start your queue, you won't process much. This change adds external links to the Queue backends that have Active Job specific docs.

Correct spelling is "Esperanto": 

https://en.wikipedia.org/wiki/Esperanto

A section explaining how to pass arguments to Jobs has been added.

[ci skip] How to pass arguments to ActiveJob Jobs

Removed the "how to pass arguments" from what you will know section

[ci skip] improving Enqueue Job section

Using GuestsCleanupJob rather than MyJob for coherence.

[ci skip] Passing args section merged with enqueuing jobs

Passing args is now explained through examples withing Enqueuing the Jobs section

[ci skip] Unnecessary example removed

[ci skip] Typo fixed (missing as)

When `#perform_later` is called the locale isn't stored on the
queue, which results in a locale reset when the job is performed.

An example of the problem:

    I18n.locale = 'de'
    HelloJob.perform_now # german message, correct

but

    I18n.locale = 'de'
    HelloJob.perform_later # english message, incorrect

This PR attaches the current I18n.locale to every job during the
serialization process. It is then restored during deserialization
and used to perform the job with the correct locale.

It falls back to the default locale if no serialized locale is
found in order to provide backward compatibility with previously
stored jobs. It is not necessary to clear the queue for the update.

[ci skip]

By default Rails automaticaly loads all files under the app directory

Extended 'Active Job Basics' edge guide with more detailed information and an additional step [ci skip]
Normalized use of 'queueing'/'queuing' in the document.

[ci skip]

- Changed `IN` to `ON` in all note sentences in guides.

Before: http://take.ms/z39h2
After: http://take.ms/Mo0G3

References #18148.

Now displays as underscore, and not an empty string, when converted from markdown to HTML.
Escaped the underscore per http://daringfireball.net/projects/markdown/syntax#em
Fixes rails/rails#18009

[ci skip]

- Added ActiveJob::Base#queue_name_delimiter to allow for
  developers using ActiveJob to change the delimiter from the default
  ('_') to whatever else they may be using (e.g., '.', '-', ...).

- Updated source guide to include a blurb about the delimiter.

* Fix a typo
* Remove references to Rails version
* Remove an extra whitespace