feat: add RSS Feed for /release-notes

[azu]

This PR add a rss feed for release notes using https://v2-0-1.11ty.dev/docs/plugins/rss/

ref #6

Test Plan

• Check https://validator.w3.org/feed/ result
• Check Local RSS Reader can view the feed

https://reederapp.com/ can view it

[captainbrosset]

Thanks so much. I'll test this as soon as I can and merge.

[captainbrosset]

Tested it, loved it, merged it. Thanks a million.

[slorber]

Thanks for the RSS feed. Seems to work fine for monthly updates.

In my case I'd prefer the ability to follow individual features in real-time.
Wouldn't it be worth it to add a second feed based on this page?
https://web-platform-dx.github.io/web-features-explorer/recent/

[captainbrosset]

Yes, having a feed for the recent and baseline pages is also planned, see #6.
Having a RSS feed for individual features also seems interesting. I've been experimenting with a visual timeline idea in #17, and that view could be available as a feed as well, so people can subscribe to individual features.