Revert "remove node_modules"

This reverts commit 2fb5731f23.

node_modules/escape-string-regexp/readme.md

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+# escape-string-regexp [![Build Status](https://travis-ci.org/sindresorhus/escape-string-regexp.svg?branch=master)](https://travis-ci.org/sindresorhus/escape-string-regexp)
+
+> Escape RegExp special characters
+
+
+## Install
+
+```
+$ npm install --save escape-string-regexp
+```
+
+
+## Usage
+
+```js
+const escapeStringRegexp = require('escape-string-regexp');
+
+const escapedString = escapeStringRegexp('how much $ for a unicorn?');
+//=> 'how much \$ for a unicorn\?'
+
+new RegExp(escapedString);
+```
+
+
+## License
+
+MIT © [Sindre Sorhus](http://sindresorhus.com)