feat(HelpButton): Mobile support.

config.js

     // the menu has option to flip the locally seen video for local presentations
     // disableLocalVideoFlip: false
 
+    // If specified a 'Help' button will be displayed in the overflow menu with a link to the specified URL for
+    // user documentation.
+    // userDocumentationURL: 'https://docs.example.com/video-meetings.html'
+
     // List of undocumented settings used in jitsi-meet
     /**
      _immediateReloadThreshold

interface_config.js

      */
     AUTO_PIN_LATEST_SCREEN_SHARE: 'remote-only'
 
-    /**
-     * The link to the user documentation.
-     */
-    // HELP_LINK: 'https://docs.example.com/video-meetings.html',
-
-
     /**
      * How many columns the tile view can expand to. The respected range is
      * between 1 and 5.

react/features/base/util/index.js

 export * from './helpers';
 export * from './httpUtils';
 export * from './loadScript';
+export * from './openURLInBrowser';
 export * from './uri';

react/features/base/util/logger.js

+// @flow
+
+import { getLogger } from '../logging/functions';
+
+export default getLogger('features/base/util');

react/features/base/util/openURLInBrowser.native.js

+// @flow
+
+import { Linking } from 'react-native';
+
+import logger from './logger';
+
+/**
+ * Opens URL in the browser.
+ *
+ * @param {string} url - The URL to be opened.
+ * @returns {void}
+ */
+export function openURLInBrowser(url: string) {
+    Linking.openURL(url).catch(error => {
+        logger.error(`An error occurred while trying to open ${url}`, error);
+    });
+}

react/features/base/util/openURLInBrowser.web.js

+// @flow
+
+/**
+ * Opens URL in the browser.
+ *
+ * @param {string} url - The URL to be opened.
+ * @returns {void}
+ */
+export function openURLInBrowser(url: string) {
+    window.open(url, '', 'noopener');
+}

react/features/toolbox/components/HelpButton.js

+// @flow
+
+import { createToolbarEvent, sendAnalytics } from '../../analytics';
+import { translate } from '../../base/i18n';
+import { IconHelp } from '../../base/icons';
+import { connect } from '../../base/redux';
+import { openURLInBrowser } from '../../base/util';
+import { AbstractButton, type AbstractButtonProps } from '../../base/toolbox';
+
+
+type Props = AbstractButtonProps & {
+
+    /**
+     * The URL to the user documenation.
+     */
+    _userDocumentationURL: string
+};
+
+/**
+ * Implements an {@link AbstractButton} to open the user documentation in a new window.
+ */
+class HelpButton extends AbstractButton<Props, *> {
+    accessibilityLabel = 'toolbar.accessibilityLabel.help';
+    icon = IconHelp;
+    label = 'toolbar.help';
+
+    /**
+     * Handles clicking / pressing the button, and opens a new window with the user documentation.
+     *
+     * @private
+     * @returns {void}
+     */
+    _handleClick() {
+        sendAnalytics(createToolbarEvent('help.pressed'));
+        openURLInBrowser(this.props._userDocumentationURL);
+    }
+}
+
+
+/**
+ * Maps part of the redux state to the component's props.
+ *
+ * @param {Object} state - The redux store/state.
+ * @returns {Object}
+ */
+function _mapStateToProps(state: Object) {
+    const { userDocumentationURL } = state['features/base/config'];
+    const visible = typeof userDocumentationURL === 'string';
+
+    return {
+        _userDocumentationURL: userDocumentationURL,
+        visible
+    };
+}
+
+export default translate(connect(_mapStateToProps)(HelpButton));

react/features/toolbox/components/native/OverflowMenu.js

 import { TileViewButton } from '../../../video-layout';
 
 import AudioOnlyButton from './AudioOnlyButton';
+import HelpButton from '../HelpButton';
 import RaiseHandButton from './RaiseHandButton';
 import ToggleCameraButton from './ToggleCameraButton';
 
                 }
                 <RaiseHandButton { ...buttonProps } />
                 <SharedDocumentButton { ...buttonProps } />
+                <HelpButton { ...buttonProps } />
             </BottomSheet>
         );
     }

react/features/toolbox/components/web/HelpButton.js

-// @flow
-
-import { createToolbarEvent, sendAnalytics } from '../../../analytics';
-import { translate } from '../../../base/i18n';
-import { IconHelp } from '../../../base/icons';
-import { AbstractButton, type AbstractButtonProps } from '../../../base/toolbox';
-
-declare var interfaceConfig: Object;
-
-/**
- * Implements an {@link AbstractButton} to open the user documentation in a new window.
- */
-class HelpButton extends AbstractButton<AbstractButtonProps, *> {
-    accessibilityLabel = 'toolbar.accessibilityLabel.help';
-    icon = IconHelp;
-    label = 'toolbar.help';
-
-    /**
-     * Handles clicking / pressing the button, and opens a new window with the user documentation.
-     *
-     * @private
-     * @returns {void}
-     */
-    _handleClick() {
-        sendAnalytics(createToolbarEvent('help.pressed'));
-        window.open(interfaceConfig.HELP_LINK);
-    }
-
-    /**
-     * Implements React's {@link Component#render()}.
-     *
-     * @inheritdoc
-     * @returns {React$Node}
-     */
-    render(): React$Node {
-        if (typeof interfaceConfig.HELP_LINK === 'string') {
-            return super.render();
-        }
-
-        return null;
-    }
-}
-
-export default translate(HelpButton);

react/features/toolbox/components/web/Toolbox.js

 import AudioMuteButton from '../AudioMuteButton';
 import { isToolboxVisible } from '../../functions';
 import HangupButton from '../HangupButton';
-import HelpButton from './HelpButton';
+import HelpButton from '../HelpButton';
 import OverflowMenuButton from './OverflowMenuButton';
 import OverflowMenuProfileItem from './OverflowMenuProfileItem';
 import ToolbarButton from './ToolbarButton';