refactor: make zero deps pkg

[antongolub]

• build the plugin itself with esbuild, drop tslib
• replace find-up with node API

[pradel]

while I am not against removing this dependency, I tested that code manually in various scenarios when I wrote the logic. Doing the following change might break stuff for some users, and would be pretty hard to check as I didn't write tests for all the scenarios I was covering with that logic.
I think we need a few tests to verify that everything is working as before before merging this one.

[antongolub]

I tested that code manually in various scenarios when I wrote the logic.

Which ones exactly? I added a simple unit test for the new method, it can be extended.

[pradel]

@antongolub iirc it was mostly in monorepos with various package managers and settings as it was creating some issues

[antongolub]

@pradel

We can publish a snapshot version for manual testing without merging this PR: #68