Add a goodparts badge

[richford]

We should add a goodparts badge as explained in https://github.com/dwyl/repo-badges/blob/main/README.md:

JavaScript the goodparts (code style/linting) - JavaScript Style Guide: Good Parts ... "Third Party" Code analysis services like CodeClimate (above) are really useful to have an "objective" (impartial) measure for the complexity/maintainability of your codebase, however you may want to take code-style/readability to the next level by using a specific style across all your projects ... Having harmony in your codebase is really useful/practical because it reduces the "thinking time". People working on the project need in order to understand (and thus maintain/extend) existing code. There are a few JavaScript "style guides" which help you & your team write consistent JS. We like goodparts because of these reasons, however we encourage you to make up your own mind as to which style to use (preferably based on sound reasoning not fashion...)