[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

web/template/profile.tmpl

@@ -27,7 +27,12 @@
             <div class="entry">Posted <b>{{.account.StatusesCount}}</b></div>
         </div>
     </div>
-    <h2 id="recent">Latest public toots</h2>
+    <h2 id="recent">
+        <span>Latest public toots</span>
+        {{ if .rssFeed }}
+            <a href="{{ .rssFeed }}"><img class="rsslogo" src="/assets/rss.svg" alt="The orange RSS logo."/></a>
+        {{ end }}
+    </h2>
 	    {{ if not .statuses }}
         <div data-nosnippet class="nothinghere">Nothing here!</div>
         {{ else }}