Add animated mx_BetaDot atop the legacy Communities button

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) {