Transition to running action in JS instead of Docker

[haldunanil]

This PR fixes #125. Specifically, it:

• Transitions the action from a Docker-based one to a JavaScript-based one, removing all Docker related files
• Uses the @vercel/ncc library to precompile the source code, including all node_modules, into a dist/index.js file, meaning no install/compile necessary when running the action
• Substantially reduces time for a single run (from approx ~2 minutes/run to ~10 seconds/run)

NOTE: This PR avoids making any changes beyond what is necessary to make the action work in a JS environment. As a result, new features like action inputs are not included.

[haldunanil]

@pascalgn this is ready for review :)

[pascalgn]

Really nice PR, thanks! It's merged now and released as v0.13.0 👍

[haldunanil]

Yay, that's awesome, thanks @pascalgn ! :)