Add jp 0.1

This pull request adds a formula for [jp](/paulhammond/jp) - a JSON prettifier written in Go.

I cannot find any other examples of go code in homebrew that follow the new no-binary-package rules. Go's build chain doesn't like installing code that it hasn't downloaded itself so the build process isn't as clean as it would ideally be. Fortunately jp doesn't have any external dependencies, you might find that other go projects in the future are not so easy to package.

See #21588 and #21576 for previous attempts to get an acceptable formula here.