Add announcements (#12662)

* Add announcements

Fix #11006

* Add reactions to announcements

* Add admin UI for announcements

* Add unit tests

* Fix issues

- Add `with_dismissed` param to announcements API
- Fix end date not being formatted when time range is given
- Fix announcement delete causing reactions to send streaming updates
- Fix announcements container growing too wide and mascot too small
- Fix `all_day` being settable when no time range is given
- Change text "Update" to "Announcement"

* Fix scheduler unpublishing announcements before they are due

* Fix filter params not being passed to announcements filter

config/locales/simple_form.en.yml

@@ -14,6 +14,12 @@ en:
         text_html: Optional. You can use toot syntax. You can <a href="%{path}">add warning presets</a> to save time
         type_html: Choose what to do with <strong>%{acct}</strong>
         warning_preset_id: Optional. You can still add custom text to end of the preset
+      announcement:
+        all_day: When checked, only the dates of the time range will be displayed
+        ends_at: Optional. Announcement will be automatically unpublished at this time
+        scheduled_at: Leave blank to publish the announcement immediately
+        starts_at: Optional. In case your announcement is bound to a specific time range
+        text: You can use toot syntax. Please be mindful of the space the announcement will take up on the user's screen
       defaults:
         autofollow: People who sign up through the invite will automatically follow you
         avatar: PNG, GIF or JPG. At most %{size}. Will be downscaled to %{dimensions}px
@@ -83,6 +89,12 @@ en:
           silence: Silence
           suspend: Suspend and irreversibly delete account data
         warning_preset_id: Use a warning preset
+      announcement:
+        all_day: All-day event
+        ends_at: End of event
+        scheduled_at: Schedule publication
+        starts_at: Begin of event
+        text: Announcement
       defaults:
         autofollow: Invite to follow your account
         avatar: Avatar