Change local and federated timelines to be in a single firehose column (#25641)

app/javascript/mastodon/features/ui/util/async-components.js

@@ -22,6 +22,10 @@ export function CommunityTimeline () {
   return import(/* webpackChunkName: "features/community_timeline" */'../../community_timeline');
 }
 
+export function Firehose () {
+  return import(/* webpackChunkName: "features/firehose" */'../../firehose');
+}
+
 export function HashtagTimeline () {
   return import(/* webpackChunkName: "features/hashtag_timeline" */'../../hashtag_timeline');
 }