* Allow moby-buildx version to be specified in devcontainer.json

Fixes #837

* Revert changes to README.md

* Address code review feedback

- Specify mobyBuildxVersion in devcontainer-feature.json with pinned and commented default value
- Bump minor version
- Leverage default value in install.sh
- Only set buildx_version_suffix when installing moby

* Handle varying distributions

* Fix typo / remove extra line