add CodeMirror's lib README to the package

src/lib/codemirror/README.md

@@ -0,0 +1,35 @@
+# CodeMirror
+[![Build Status](https://travis-ci.org/codemirror/CodeMirror.svg)](https://travis-ci.org/codemirror/CodeMirror)
+[![NPM version](https://img.shields.io/npm/v/codemirror.svg)](https://www.npmjs.org/package/codemirror)
+[![Join the chat at https://gitter.im/codemirror/CodeMirror](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/codemirror/CodeMirror)  
+[Funding status: ![maintainer happiness](https://marijnhaverbeke.nl/fund/status_s.png?again)](https://marijnhaverbeke.nl/fund/)
+
+CodeMirror is a versatile text editor implemented in JavaScript for
+the browser. It is specialized for editing code, and comes with over
+100 language modes and various addons that implement more advanced
+editing functionality. Every language comes with fully-featured code
+and syntax highlighting to help with reading and editing complex code.
+
+A rich programming API and a CSS theming system are available for
+customizing CodeMirror to fit your application, and extending it with
+new functionality.
+
+You can find more information (and the
+[manual](http://codemirror.net/doc/manual.html)) on the [project
+page](http://codemirror.net). For questions and discussion, use the
+[discussion forum](https://discuss.codemirror.net/).
+
+See
+[CONTRIBUTING.md](https://github.com/codemirror/CodeMirror/blob/master/CONTRIBUTING.md)
+for contributing guidelines.
+
+The CodeMirror community aims to be welcoming to everybody. We use the
+[Contributor Covenant
+(1.1)](http://contributor-covenant.org/version/1/1/0/) as our code of
+conduct.
+
+### Quickstart
+
+To build the project, make sure you have Node.js installed (at least version 6)
+and then `npm install`. To run, just open `index.html` in your
+browser (you don't need to run a webserver). Run the tests with `npm test`.