Remove yarn.lock file and test folder from published package

[simondel]

I'm submitting a ...

• [ ] bug report
• [x] feature request
• [ ] support request

The latest version of the published package includes a yarn.lock file and all tests. These are not required by someone who is implementing this component, so they can be omitted.

I could add this to the .npmignore if you'd like.

[vcarl]

Hey @simondel this slipped past me! This is a good idea, I'd love to see a PR if you have some time.