FR: Support for NX workspace plugin

**Is your feature request related to a problem? Please describe.**
We use NX to manage our Workspace. The `node-workspace` plugin isn't resulting in the correct dep tree based on our set up. We have packages that depend on others, but its not resulting in that when using the `node-workspce` plugin.
**Describe the solution you'd like**
We'd like to be able to write our own custom plugin to handle this. If you'd like to add support for NX, that would be nice too
**Describe alternatives you've considered**
Only other alternative was switching to another package, but we like what `release-please` offers over others like semantic-release
**Additional context**
NONE