Support for `cargo binstall`

There are GitHub Actions that produce `pgdo` binaries for tagged commits / releases, but [`cargo binstall`](https://github.com/cargo-bins/cargo-binstall) does not automatically discover them. It would be nice to avoid compiling `pgdo-cli` every time there's an upgrade. [This page](https://github.com/cargo-bins/cargo-binstall/blob/main/SUPPORT.md) has instructions on how to make it happen.