Add GH Actions workflow for testing C/C++ examples

[nightlark]

Converted the existing Azure Pipelines workflow to run on GitHub Actions.

[trevorhardy]

@nightlark, I see you've marked this as "draft"; what is the next step in getting these converted over to GitHub Actions?

[nightlark]

The CMake configuration errors need to be resolved to the point where it isn't failing due to issues finding tools that need installing on the VM. Right now a copy of Ninja looks like it needs to get installed on some platforms.

[trevorhardy]

The CMake configuration errors need to be resolved to the point where it isn't failing due to issues finding tools that need installing on the VM. Right now a copy of Ninja looks like it needs to get installed on some platforms.

This is outside my skill set; is this something you can tackle?

[nightlark]

I think it's at that point now. It found all the build tools needed, and is now failing because the examples are asking for HELICS v2.