Add subcommand for changing ZMK versions

[caksoylar]

A zmk version command might be useful to update the repo to change ZMK versions. The tags or releases can be fetched from GH API (with an additional development one tracking main, and in the future, this can help us decouple the config template repo from the latest version updates as well.

In addition, zmk init can accept a --zmk-version parameter to initialize with a specific version.

[joelspadin]

Seems like a good idea to me. PR is up for review.