Add GitHub Actions

[yonip23]

On push:

• Test
• Formatter
• Prettier

Manual dispatch / on tag:

• Publish (maybe with automatic version update?)

[yonip23]

on push actions are done, need a release job.
This is more complicated, since the steps are:

• update version in all 3 Cargo.tomls, including the inter-dependencies
• commit
• publish proclock-api
• publish proclock-macro
• publish proclock
• push

[yonip23]

update: found this cargo-release crate which makes it so much easier
So the job needs to:

1. get major/minor/patch... as an input
   maybe add an explicit version option
2. install cargo-release
3. run cargo release ${{input}} --exclude tests -x

--
Need to figure out how to deal with breaking changes across crates - this will fail the tests until you publish a version...