fix windows github actions ci

[vivekmalneedi]

This PR fixes the windows github actions CI build by removing bin/install.js and instead using the build script in package.json to invoke tree-sitter and node-gyp directly as is done in other tree-sitter grammars.

This should also fix #41

I also edited the github actions workflows to run on pull requests, in an attempt to show that this PR works, since the travis CI doesn't test windows, but it seems editing workflows requires maintainer approval. On my own fork all github actions workflows were passing before I disabled running the CI on push for non-master branches since I'm pretty sure that without the restriction it will double run CI on a push to a pr.