Add alternate for RSS (#7436)

app/views/accounts/show.html.haml

@@ -8,6 +8,7 @@
     %meta{ name: 'robots', content: 'noindex' }/
 
   %link{ rel: 'salmon', href: api_salmon_url(@account.id) }/
+  %link{ rel: 'alternate', type: 'application/rss+xml', href: account_url(@account, format: 'rss') }/
   %link{ rel: 'alternate', type: 'application/atom+xml', href: account_url(@account, format: 'atom') }/
   %link{ rel: 'alternate', type: 'application/activity+json', href: ActivityPub::TagManager.instance.uri_for(@account) }/
 

app/views/tags/show.html.haml

@@ -2,6 +2,8 @@
   = "##{@tag.name}"
 
 - content_for :header_tags do
+  %link{ rel: 'alternate', type: 'application/rss+xml', href: tag_url(@tag, format: 'rss') }/
+
   %script#initial-state{ type: 'application/json' }!= json_escape(@initial_state_json)
   = javascript_pack_tag 'about', integrity: true, crossorigin: 'anonymous'
   = render 'og'