Add Docker support and upgrade failing sharp

[JohnnyMarnell]

Thanks for these great repos 🙏🏻

Had a bit of trouble getting this to run on my Macs, and I think adding Docker support can help to reduce variables with errors and troubleshooting (e.g. node-gyp failures, differing dependency versions, differing architectures). Plus this could help CI/CD, or simple case of not wanting to install Node.JS dependencies and ffmpeg itself.

Also discovered sharp dependency needed to be upgraded (breaking on multiple versions of node + arch's), see here

Tested with Docker v20.10.11, OS X Monterey, M1 / arm64, and Docker v19.03.13, OS X Catalina, Intel

[JohnnyMarnell]

@transitive-bullshit any thoughts?