Adds Babel plugin babel-plugin-optimize-react

Created by: trueadm

This PR adds a Babel 7 plugin that aims to optimize certain React patterns that aren't as optimized as they might be. For example, with this plugin the following output is optimized as shown:

// Original
var _useState = Object(react__WEBPACK_IMPORTED_MODULE_1_["useState"])(Math.random()),
    _State2 = Object(_Users_gaearon_p_create_rreact_app_node_modules_babel_runtime_helpers_esm_sliceToArray_WEBPACK_IMPORTED_MODULE_0__["default"])(_useState, 1),
    value = _useState2[0];
    
// With this plugin
var useState = react__WEBPACK_IMPORTED_MODULE_1_.useState;
var __ref__0 = useState(Math.random());
var value = __ref__0[0];

Named imports for React get transformed

// Original
import React, {useState} from 'react';

// With this plugin
import React from 'react';
const {useState} = React;

Array destructuring transform for React's built-in hooks

// Original
const [counter, setCounter] = useState(0);

// With this plugin
const __ref__0 = useState(0);
const counter = __ref__0[0];
const setCounter = __ref__0[1];

React.createElement becomes a hoisted constant

// Original
import React from 'react';

function MyComponent() {
  return React.createElement('div', null, 'Hello world');
}

// With this plugin
import React from 'react';
const __reactCreateElement__ = React.createElement;

function MyComponent() {
  return __reactCreateElement__('div', null, 'Hello world');
}