Gets a video file's playback URL from the Media Manager.
The getVideoPlaybackUrl() function returns a Promise that resolves to the
specified video file's playback URL.
The file's Wix media URL in the following format: 'wix:image://v1//#originWidth=&originHeight=[&watermark=]'.
Note: This replaces the old fileName parameter. fileName will continue to work, but we recommend that you use the updated fileUrl parameter instead.
The format of the URL to get. Either "hls" or "dash".