Tasks: Add task for publishing to npm

Fixes #3

There's an open question about tags in the underlying issue (#3), so this PR is therefore incomplete. But I wanted to share that anyway.

I ran this with a test repo, where the npm task does nothing but logging. I would like to create a test project where we can test this script, publishing files to the fake cdn, but to actual npm. Should be a GitHub repo with a few issues and contributors, to test those (missing) features as well.