feat(Filmstrip): accessibility label for toggle filmstrip button

lang/main.json

             "speakerStats": "Toggle speaker statistics",
             "tileView": "Toggle tile view",
             "toggleCamera": "Toggle camera",
+            "toggleFilmstrip": "Toggle filmstrip",
             "videomute": "Toggle mute video",
             "videoblur": "Toggle video blur"
         },

react/features/filmstrip/components/web/Filmstrip.js

     sendAnalytics
 } from '../../../analytics';
 import { Icon, IconMenuDown, IconMenuUp } from '../../../base/icons';
+import { translate } from '../../../base/i18n';
 import { connect } from '../../../base/redux';
 import { dockToolbox } from '../../../toolbox';
 
     /**
      * The redux {@code dispatch} function.
      */
-    dispatch: Dispatch<any>
+    dispatch: Dispatch<any>,
+
+    /**
+     * Invoked to obtain translated strings.
+     */
+    t: Function
 };
 
 /**
      */
     _renderToggleButton() {
         const icon = this.props._visible ? IconMenuDown : IconMenuUp;
+        const { t } = this.props;
 
         return (
             <div className = 'filmstrip__toolbar'>
                 <button
+                    aria-label = { t('toolbar.accessibilityLabel.toggleFilmstrip') }
                     id = 'toggleFilmstripButton'
                     onClick = { this._onToolbarToggleFilmstrip }>
                     <Icon src = { icon } />
     };
 }
 
-export default connect(_mapStateToProps)(Filmstrip);
+export default translate(connect(_mapStateToProps)(Filmstrip));