Add support to crop / zoom into a video stream. Useful on watch OS.
**Is your feature request related to a problem? Please describe:**
I often use the integration with my watch to keep an eye on the crib, this works well, but I can't zoom in on the area of interest and thus 80% of my watch surface is wasted / makes it hard to see area of interest at a glance.

**Describe the solution you'd like:**
I would like to define an area to be cropped / zoomed into. Ideally with a ratio which would work well on the watch (3:4 ratio).

**Describe alternatives you've considered:**
I've considered working with ffmpeg to crop and reencode the video stream, and using another plugin to make the cropped stream available to homekit. I'm still working on seeing if this will work

**Additional context:**
If you've ever seen 16:9 video on the watch, you've seen that half the screen is wasted on black bars.
