Feed embedding and information

[nuest]

@nuest cloned issue ifgi/optimetaPortal#23 on 2022-06-17. Updated here.

---

• HTML page /feeds lists the available feeds
• feeds are embedded in the HTML header of the index page

[nuest]

Here are some links to get started with the embedding of feeds:

• https://zapier.com/blog/how-to-find-rss-feed-url/ (from a reader perspective)
• https://www.petefreitag.com/blog/rss-autodiscovery/
• https://www.hashbangcode.com/article/linking-rss-or-atom-feed-html-document

[nuest]

Closed in #210