Requirements missing/wrong

[gurka]

Trying to build jellyfin for the first time and I noticed a few things:

• requirements.txt has the wrong package name for the python git library. git is not available in PyPI, but GitPython is, which seems to be the correct package (based on Debian's package python3-git, which links to GitPython on Github, which links to GitPython on PyPI).
• README.md should maybe mention that docker-buildx-plugin is required for the docker build

[joshuaboniface]

Good finds, let me update both.