Name
nv-codec-headers

Homepage
https://github.com/FFmpeg/nv-codec-headers

Why should this be included in the repository?
It allows building hardware accelerated FFmpeg for Nvidia GPU's.
From mpv readme:

For good nvidia support on Linux, make sure nv-codec-headers is installed and can be found by configure.

Is it Open Source
Yes

Who and how many users do you anticipate will use this software?
Most of the people with Nvidia GPU.

Link to source tarball/zip file
https://github.com/FFmpeg/nv-codec-headers/releases/download/n8.2.15.6/nv-codec-headers-8.2.15.6.tar.gz