Add GitHub Actions configuration

[robinkrahl]

This patch adds a configuration for GitHub Actions that builds and tests nitrocli with the MSRV, stable, beta and nightly Rust, calls clippy and rustfmt and checks the license annotations with reuse-tool.

(Previous discussion at #148.)

[robinkrahl]

Build logs for this PR.

[robinkrahl]

Notes:

• We might want to add caching using actions/cache.
• Most examples use cargo check instead of cargo build. But as our build involves linking to a shared library (which AFAIK is skipped for check), I think performing the full build is better for us.

[d-e-s-o]

Fabulous stuff! Thanks for looking into that.

• We might want to add caching using actions/cache.

We can do that. Let's first move forward with what we have. It seems to already be a hefty speed boost.

• Most examples use cargo check instead of cargo build. But as our build involves linking to a shared library (which AFAIK is skipped for check), I think performing the full build is better for us.

:+1:

[d-e-s-o]

Will merge tomorrow.

[d-e-s-o]

Merged.

[robinkrahl]

Thanks for merging! By the way, I also tested macOS, but we get an exception when trying to run the tests.

[d-e-s-o]

Thanks for merging! By the way, I also tested macOS, but we get an exception when trying to run the tests.

Hm, interesting. No idea how to debug this issue, to be honest. We may still need someone with a macOS at hand.