Initial CI: Check style and build

[EwoutH]

First of all, awesome project!

I wrote a quick CI setup for checking style and building Atom. It currently runs a basic format and lint job, and a build job on Ubuntu, macOS and Windows.

As you can see, rustfmt already catched two trailing whitespaces!

There are a lot of possibilities from here:

• Cargo bench, test, check, doc, etc.
• Cross compilation to different targets (arm64 for example)
• Compilations on different toolchains (beta, nightly)
• Running rustfmt and clippy with more arguments

GitHub Actions needs to be activated.

Let me know what you think!

[EwoutH]

@adam-mcdaniel If you would like anything changed or explained please let me know, now this CI configuration is still fresh in my memory :)

[EwoutH]

@adam-mcdaniel Please let me know if you are interested in some CI for this project! Otherwise I will close this PR.

[EwoutH]

I'm doing some cleanup of old, open PRs. If you would like to get these changes in, please leave a reply or review.

In two weeks I will close this PR if no reaction received.

[EwoutH]

Closing due to lack of response.