Add animated mx_BetaDot atop the legacy Communities button

src/components/structures/GroupFilterPanel.js

@@ -123,12 +123,19 @@ class GroupFilterPanel extends React.Component {
             mx_GroupFilterPanel_items_selected: itemsSelected,
         });
 
+        let betaDot;
+        if (!SettingsStore.getValue("feature_spaces") && !localStorage.getItem("mx_seenSpacesBeta")) {
+            betaDot = <div className="mx_BetaDot" />;
+        }
+
         let createButton = (
             <ActionButton
                 tooltip
                 label={_t("Communities")}
                 action="toggle_my_groups"
-                className="mx_TagTile mx_TagTile_plus" />
+                className="mx_TagTile mx_TagTile_plus">
+                { betaDot }
+            </ActionButton>
         );
 
         if (SettingsStore.getValue("feature_communities_v2_prototypes")) {

src/components/structures/MatrixChat.tsx

@@ -740,6 +740,8 @@ export default class MatrixChat extends React.PureComponent<IProps, IState> {
                 this.showScreenAfterLogin();
                 break;
             case 'toggle_my_groups':
+                // persist that the user has interacted with this, use it to dismiss the beta dot
+                localStorage.setItem("mx_seenSpacesBeta", "1");
                 // We just dispatch the page change rather than have to worry about
                 // what the logic is for each of these branches.
                 if (this.state.page_type === PageTypes.MyGroups) {