Contributor Readme

[jguffey]

Hi there, nice module! I'm forking it to try to add the ability to wait for an element to load before taking the screenshot.

However, I'm unsure if this repo is already compiled, or if there are missing buildscripts? I see a Makefile, but running it errors out unless you have some dependencies (GJSLINT, lint, .PHONY) installed.

At a minimum, it would be nice to know how to build the package.

Thanks for the hard work!