Add some recommended config files to use (as is or as basis) for setting
up [remote development using docker containers][1] with VSCode. This is
an opt-in feature. See `.devcontainer/README.md` for more info.
The configuration can be further tweaked/improved, but is a good
starting point.
[1]: https://code.visualstudio.com/docs/remote/containers
PR Close#30450
