Cleanup published package

[krzkaczor]

Probably you don't want to include .vscode and original ts files in a published package.

I highly recommend using package.json's files instead of .npmignore.

[krzkaczor]

One more thing: you explicitly target node 10 (in package.json) yet transpiled code targets some ancient architecture (es5?) making code slower and harder to read (I often read transpiled output while debugging).

[sz-piotr]

This is a valid point. We should update the build scripts to address that