Add the ability to generate zoom animations

[rosslh]

There should be a button and modal similar to the "save image" functionality. The options should be:

• Kind
  • Zoom in to this location
  • Zoom out from this location
• Height (px)
• Width (px)
• Duration (seconds)
• Frame rate (fps)

It should generate an MP4 video. The video generation should be done in a web worker to avoid blocking the main thread.