Update npmignore

I've added a number of entries to the `.npmignore` that shouldn't be needed in the npm package (and sorted them alphabetically, folders first, for clarity).

But I'm wondering if tests and test resources are needed in the npm package? IMO those are things interested people will take from Github if they want, it's just wasting bandwidth (with tests the package gzipped is ~440 kB, without them < 20 kB). What do you think guys?