make number of displayed reactions a setting

This adds an extra item to the local settings for
specifying the number of reactions shown in toots.
The detailed status view always shows all
reactions.

app/javascript/flavours/glitch/components/status.jsx

@@ -828,6 +828,7 @@ class Status extends ImmutablePureComponent {
           <StatusReactions
             statusId={status.get('id')}
             reactions={status.get('reactions')}
+            numVisible={settings.get('num_visible_reactions')}
             addReaction={this.props.onReactionAdd}
             removeReaction={this.props.onReactionRemove}
             emojiMap={this.props.emojiMap}