[feature] Add opt-in RSS feed for account's latest Public posts (#897)

* start adding rss functionality

* add gorilla/feeds dependency

* first bash at building rss feed
still needs work, this is an interim commit

* tidy up a bit

* add publicOnly option to GetAccountLastPosted

* implement rss endpoint

* fix test

* add initial user docs for rss

* update rss logo

* docs update

* add rssFeed to frontend

* feed -> feed.rss

* enableRSS

* increase rss logo size a lil bit

* add rss toggle

* move emojify to text package

* fiddle with rss feed formatting

* add Text field to test statuses

* move status to rss item to typeconverter

* update bun schema for enablerss

* simplify 304 checking

* assume account not rss

* update tests

* update swagger docs

* allow more characters in title, trim nicer

* update last posted to be more consistent

internal/api/mime.go

@@ -25,6 +25,7 @@ type MIME string
 const (
 	AppJSON           MIME = `application/json`
 	AppXML            MIME = `application/xml`
+	AppRSSXML         MIME = `application/rss+xml`
 	AppActivityJSON   MIME = `application/activity+json`
 	AppActivityLDJSON MIME = `application/ld+json; profile="https://www.w3.org/ns/activitystreams"`
 	AppForm           MIME = `application/x-www-form-urlencoded`