Add 'm.youtube.com/...' to be recognized as a YouTube link in the embedded post content. (#4114)

webapp/components/youtube_video.jsx

@@ -5,7 +5,7 @@ import ChannelStore from 'stores/channel_store.jsx';
 import WebClient from 'client/web_client.jsx';
 import * as Utils from 'utils/utils.jsx';
 
-const ytRegex = /(?:http|https):\/\/(?:www\.)?(?:(?:youtube\.com\/(?:(?:v\/)|(\/u\/\w\/)|(?:(?:watch|embed\/watch)(?:\/|.*v=))|(?:embed\/)|(?:user\/[^\/]+\/u\/[0-9]\/)))|(?:youtu\.be\/))([^#&\?]*)/;
+const ytRegex = /(?:http|https):\/\/(?:www\.|m\.)?(?:(?:youtube\.com\/(?:(?:v\/)|(?:(?:watch|embed\/watch)(?:\/|.*v=))|(?:embed\/)|(?:user\/[^\/]+\/u\/[0-9]\/)))|(?:youtu\.be\/))([^#&\?]*)/;
 
 import React from 'react';