Document podman/docker

Working with podman/docker info would also be useful to add in the Readme or Wiki:
#55

_Originally posted by @bam80 in https://github.com/flathub/com.visualstudio.code/issues/324#issuecomment-4597474347_

There are actually a few pretty much ready instructions on the link above, as:
https://gist.github.com/lbssousa/bb081e35d483520928033b2797133d5e

@nikodunk

Review the linked gist, issue #55, and the existing README or Wiki to identify where container-related guidance belongs. Add accurate Podman/Docker instructions based on the referenced material, and consider the work complete when the guidance is published in the chosen documentation location and is understandable to users.

索引モデルが issue の本文から書いたものです。