[Glitch] Add ActivityPub actor representing the entire server

Port SCSS changes from 730c4053d6

Signed-off-by: Thibaut Girka <thib@sitedethib.com>

app/javascript/flavours/glitch/styles/containers.scss

@@ -147,6 +147,10 @@
     min-height: 100%;
   }
 
+  .flash-message {
+    margin-bottom: 10px;
+  }
+
   @media screen and (max-width: 738px) {
     grid-template-columns: minmax(0, 50%) minmax(0, 50%);