Auto merge of #10212 - SamMorrowDrums:patch-1, r=alexcrichton
Auto merge of #10212 - SamMorrowDrums:patch-1, r=alexcrichton

[docs] Adds basic CI yaml for GitHub Actions

Currently there is no documentation for GitHub Actions, so I have attempted to add an Actions Workflow that is equivalent to the other CI snippets in the file. You can view a successful run of this Action in my repo for experimenting with this here: https://github.com/SamMorrowDrums/rust-action-test/actions/runs/1593666172

The Rust code I tested it with is just the boilerplate from `cargo init`.

rustyhorde/cargo,nipunn1313/cargo,eminence/cargo,rustyhorde/cargo,eminence/cargo,nipunn1313/cargo,rustyhorde/cargo,eminence/cargo,eminence/cargo,nipunn1313/cargo,rust-lang/cargo,rust-lang/cargo,rustyhorde/cargo,rust-lang/cargo,nipunn1313/cargo,rust-lang/cargo