cc @existentialism

everything in https://github.com/babel/babel.github.io/tree/master/docs/plugins

{% include package_readme.html %}

links to the readme in https://github.com/babel/babel/tree/master/packages such as https://github.com/babel/babel/tree/master/packages/babel-plugin-transform-es2015-arrow-functions

Meaning make sure it has some kind of in/out example code + maybe a REPL link if it makes sense. Same with each option if it's helpful

We should also probably make sure the format of each readme is consistent (in/out, install, usage, options)