Refs #202 -- Filter timeline based on component

[blighj]

This comes out of discussion on #202, but it is not a solution to that issue.
The goal here is to be able to subscribe via RSS to the timeline of ticket events for a specfic component(s).
The design goal is not a general solution for all users but for engaged/expert users who follow a particilar area of the codebase, like ORM, or in my case staticfiles.

It was inspired by @sarahboyce's forum post on review teams per area. The suggestion of subscribing to a component struck a cord with me, and RSS is the tool I would use, An assumption is that others in the target group still use RSS, which I've no evidence for.

With this in place it would be possible to subscribe via an RSS reader and get updates of activity in your desired copmonents. There is no UI for this, it's assumed that the links would be published in the likes of a forum post or discord etc. I'm not hiding it from the general public, but not spending the effort building a UI and explaing it, as I think it is not relevant for them. This keeps the code change small and that bit more maintainable.

If this is a runner, I'm not familiar with how caching is configured for code.djangoproject so it would need to be considered how that would affect the goal.

[sarahboyce]

Thank you so much for picking this up!

I think we could at the very least add these links to the Trac wiki homepage: https://code.djangoproject.com/
But we can also add them to Django's RSS feeds: https://www.djangoproject.com/community/

Ideally this filter would exist in the timeline filter UI but that might be really challenging

[sarahboyce]

@bmispelon I tested locally and this works for me, let me know if you're happy for me to merge or if you also want to look 👍