docs(faq): add FAQ question about RTMP url (#3899)

docs/faq.md

@@ -15,6 +15,7 @@
   * [If you don't think you can fix the issue or add the feature](#if-you-dont-think-you-can-fix-the-issue-or-add-the-feature)
 * [Q: What is a reduced test case?](#q-what-is-a-reduced-test-case)
 * [Q: What media formats does video.js support?](#q-what-media-formats-does-videojs-support)
+* [Q: How can I play RTMP video in video.js?](#q-how-can-i-play-rtmp-video-in-videojs)
 * [Q: How can I hide the links to my video/subtitles/audio/tracks?](#q-how-can-i-hide-the-links-to-my-videosubtitlesaudiotracks)
 * [Q: What is a plugin?](#q-what-is-a-plugin)
 * [Q: How do I make a plugin for video.js?](#q-how-do-i-make-a-plugin-for-videojs)
@@ -116,6 +117,15 @@ techs made available to video.js. For example, video.js 5 includes the Flash tec
 enables the playback of FLV video where the Flash plugin is available. For more information
 on media formats see the [troubleshooting guide][troubleshooting].
 
+## Q: How can I play RTMP video in video.js?
+
+Make sure that the Flash tech is available -- RTMP is not playable on browsers without Flash including mobile. Then, just set the rtmp source with
+an appropriate type -- `rtmp/mp4` or `rtmp/flv`.
+The main thing to be aware of is that video.js splits the connection url and stream name with the `&` character.
+So, you'd want to update the url to follow that format. For example: `rtmp://example.com/live&foo` or `rtmp://example.com/fms&mp4:path/to/file.mp4`.
+
+If the server requires query parameters for authentication, these should be added to the connection part url, for example `rtmp://example.com/live?token=1234&foo`.
+
 ## Q: How can I hide the links to my video/subtitles/audio/tracks?
 
 It's impossible to hide the network requests a browser makes and difficult to