Add simple CI pipeline via GitHub actions

[david-a-wheeler]

Create a simple CI pipeline via GitHub actions.
This does a basic "cargo test" on several different environments
and two different versions of Rust. Eventually more checks can
be added.

Signed-off-by: David A. Wheeler [email protected]

[sorear]

I didn't ask for any of this.

[david-a-wheeler]

I'm not sure I understand your comment. It's normal to always test all changes in a variety of environments, to ensure that the proposed change works.

[david-a-wheeler]

My apologies if my proposals are annoying; that isn't my intent.

I think it's important to establish an automated CI pipeline and to eliminate all warnings (including lint warnings) over time. Rust has changed over the years; I intend to change the code so it is idiomatic to current Rust usage. I also intend to propose a large number of changes over time to make this capable of doing more (including a C interface & definition checking). I also want to merge Mario's proposed change to support all Metamath proof formats.

I'd rather work with you to make all these changes. But if that's not the direction you want to go, you have every right to say no to all of it. If that isn't the direction you want to go, I'll probably just create & maintain a separate fork of the project, ensuring that everything is done in many public commits so you can cherry-pick what you like if you want to.