Support Video Capture

[AntumDeluge]

Adds video capture of viewport & audio capture of page.

🛠️ Tasks

• video capture
  • support capturing viewport only
  • support capturing entire page (will be added in different PR)
  • allow custom framerate if possible in WebAPI (will be added in different PR)
  • allow alternative codecs/containers such as MP4, OGG, etc. (may be browser dependent) (currently only WEBM is supported as tested in Firefox on Windows) (will be added in different PR)
• audio capture (may need to change sound manager to utilize AudioContext) (will be added in different PR)
  • it may require all audio being played from a single source
• slash action to start/stop
• menu button to start/stop

Completed features will be merged to master as alpha features. Remaining features will be added in a new PR or directly to master.

Related to #733