* Bump minimum Rust version to 1.60
As required by the `time` crate (`notify-rust` > `mac-notification-sys` > `time`).
* Simplify CI
Changes:
- Bump `actions/checkout` to v3, fixing a bunch of warnings.
- Replace unmaintained `actions-rs/cargo` by `dtolnay/rust-toolchain`.
- Run Rustfmt only once.
- Add support for cached dependencies (via `Swatinem/rust-cache`).
* Add Android target
Use the awesome `cross` tool for cross-compiling!
* Add FreeBSD target
