Update React transform READMEs from babel.github.io [skip ci] (#4903)

* Update React transform READMEs from babel.github.io [skip ci]

* Drop inline-elements polyfill message (move to website)

packages/babel-plugin-transform-react-jsx/README.md

@@ -2,10 +2,60 @@
 
 Turn JSX into React function calls
 
+## Example
+
+### React
+
+**In**
+
+```javascript
+var profile = <div>
+  <img src="avatar.png" className="profile" />
+  <h3>{[user.firstName, user.lastName].join(' ')}</h3>
+</div>;
+```
+
+**Out**
+
+```javascript
+var profile = React.createElement("div", null,
+  React.createElement("img", { src: "avatar.png", className: "profile" }),
+  React.createElement("h3", null, [user.firstName, user.lastName].join(" "))
+);
+```
+
+### Custom
+
+**In**
+
+```javascript
+/** @jsx dom */
+
+var { dom } = require("deku");
+
+var profile = <div>
+  <img src="avatar.png" className="profile" />
+  <h3>{[user.firstName, user.lastName].join(' ')}</h3>
+</div>;
+```
+
+**Out**
+
+```javascript
+/** @jsx dom */
+
+var dom = require("deku").dom;
+
+var profile = dom( "div", null,
+  dom("img", { src: "avatar.png", className: "profile" }),
+  dom("h3", null, [user.firstName, user.lastName].join(" "))
+);
+```
+
 ## Installation
 
 ```sh
-$ npm install babel-plugin-transform-react-jsx
+npm install babel-plugin-transform-react-jsx
 ```
 
 ## Usage
@@ -32,7 +82,7 @@ $ npm install babel-plugin-transform-react-jsx
 ### Via CLI
 
 ```sh
-$ babel --plugins transform-react-jsx script.js
+babel --plugins transform-react-jsx script.js
 ```
 
 ### Via Node API
@@ -42,3 +92,9 @@ require("babel-core").transform("code", {
   plugins: ["transform-react-jsx"]
 });
 ```
+
+## Options
+
+* `pragma` - Replace the function used when compiling JSX expressions (Defaults to `React.createElement`).
+  - Note that the `@jsx React.DOM` pragma has been deprecated as of React v0.12
+* `useBuiltIns` - When spreading props, use Object.assign instead of Babel's extend helper (Disabled by default).