Excellent and evergreen question. There is "level 1" support via the adhoc backend, that lets you run arbitrary commands (e.g., npm/yarn commands in this case) within a pants build. There are examples here:
https://github.com/pantsbuild/example-adhoc
I believe
@worried-painter-31382 is working on "level 2" support - full support for dep inference, fine-grained invalidation and so on.