Add keyboard shortcuts for LocalRecordingInfoDialog

Which key should we use? Using "L" for now.

lang/main.json

         "mute": "Mute or unmute your microphone",
         "fullScreen": "View or exit full screen",
         "videoMute": "Start or stop your camera",
-        "showSpeakerStats": "Show speaker stats"
+        "showSpeakerStats": "Show speaker stats",
+        "localRecording": "Show or hide local recording controls"
     },
     "welcomepage":{
         "accessibilityLabel": {

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

                 character: 'S',
                 exec: this._onShortcutToggleFullScreen,
                 helpDescription: 'keyboardShortcuts.fullScreen'
+            },
+            this._shouldShowButton('localrecording') && {
+                character: 'L',
+                exec: this._onToolbarToggleLocalRecordingInfoDialog,
+                helpDescription: 'keyboardShortcuts.localRecording'
             }
         ];