NIH-plug: cargo subcommand for bundling plugins

This is NIH-plug's cargo xtask command, but as a cargo subcommand. This way you can use it outside of NIH-plug projects. If you're using NIH-plug, you'll want to use the xtask integration directly instead so you don't need to worry about keeping the command up to date, see: https://github.com/robbert-vdh/nih-plug/tree/master/nih_plug_xtask.

Since this has not yet been published to crates.io, you'll need to install this using:

cargo install --git https://github.com/robbert-vdh/nih-plug.git cargo-nih-plug

Once that's installed, you can compile and bundle plugins using:

cargo nih-plug bundle <package_name> --release