The staticfiles dependency updated to support Go 1.18 generics in the
2022.1 release. This prevents the devcontainer (which has Go 1.16) from
being built. This moves the container to Fedora 36 which provides Go
1.18.
Make the devcontainer more complete for osbuild-composer by
installing more dependencies and plugins.
This enables golang and github integration by default.
Introduce Dockerfile and devcontainer.json specifying how to build and
run a containerized development environment in VSCode.
The configuration is inspired by the osbuild repo where a similar
configuration directory already exists.
