Pegjs Pretty Printer

[siefkenj]

I've been working on a Pegjs pretty printer (based on Prettier, the Javascript code formatter). You can find the code here: https://github.com/siefkenj/prettier-plugin-pegjs and there is also a playground. My hope is that it will conform to the guidelines of #248. It could potentially be modified to address #641, and seems like it might be nice to integrate into the Pegjs playground.

Comments/suggestions/contributions are welcome. I'd also be happy to move this project to the offical pegjs repo if a maintainer is interested (and once's it's debugged).