Enable "jsx-a11y/alt-text" and "jsx-a11y/label-has-associated-control" lint rules (#10361)

* enable "jsx-a11y/alt-text" lint rule

* enable "jsx-a11y/label-has-associated-control"

src/components/views/rooms/EntityTile.tsx

@@ -161,7 +161,12 @@ export default class EntityTile extends React.PureComponent<IProps, IState> {
         if (this.props.showInviteButton) {
             inviteButton = (
                 <div className="mx_EntityTile_invite">
-                    <img src={require("../../../../res/img/plus.svg").default} width="16" height="16" />
+                    <img
+                        alt={_t("Invite")}
+                        src={require("../../../../res/img/plus.svg").default}
+                        width="16"
+                        height="16"
+                    />
                 </div>
             );
         }