Changes

Add preview of automatic library support

Example plugin.yml usage:
```
    libraries:
      - com.squareup.okhttp3:okhttp:4.9.0
```

Libraries will only be accessible to plugins and their transitive depends, allowing for multiple versions of the same library to be used by different plugins.

This is a preview feature. Feedback is welcome so that it may be refined before being made widely available.
 (commit: 6a039de)