PLT-6282 Make post list stay visible when post textbox height changes (#6323)

* PLT-6282 Changed post drafts to use an action when being stored

* PLT-6282 Triggered post list to update scroll position when post draft changes

* PLT-6282 Changed SuggestionBox to complete suggestions without an event

webapp/utils/constants.jsx

@@ -92,6 +92,7 @@ export const ActionTypes = keyMirror({
     RECEIVED_ADD_MENTION: null,
     RECEIVED_POST_PINNED: null,
     RECEIVED_POST_UNPINNED: null,
+    POST_DRAFT_CHANGED: null,
 
     RECEIVED_PROFILES: null,
     RECEIVED_PROFILES_IN_TEAM: null,