Support for Nvidia GPU Accelerated Transcoding
**Is your feature request related to a problem? Please describe:**
My Homebridge server has a powerful Nvidia GPU. (GeForce 3090). Currently the Unifi Protect plugin appears to only be using CPU-based encoding.

**Describe the solution you'd like:**
I would love to be able to check a box to enable "Nvidia GPU Accelerated Transcoding" in the Unifi Protect Plugin. This option would then pass in the proper flags to the ffmpeg transcode invokation.

**Additional context:**
https://stackoverflow.com/questions/44510765/gpu-accelerated-video-processing-with-ffmpeg