Separate Out Core Components Into Individual Parts

Summary:
Will create new issue to add more information to the `Components` section of the Tutorial
since that was gutted by this change.

Fixes #8156
Closes https://github.com/facebook/react-native/pull/8256

Differential Revision: D3459601

Pulled By: JoelMarcey

fbshipit-source-id: 4038afc463bffcf8efda36d29bc7c443bbc8f4bd

docs/Basics-Component-TextInput.md

@@ -0,0 +1,28 @@
+---
+id: basics-component-textinput
+title: TextInput
+layout: docs
+category: Basics
+permalink: docs/basics-component-textinput.html
+next: basics-component-listview
+---
+
+Direct text-based user input is a foundation for many apps. Writing a post or comment on a page is a canonical example of this. [`TextInput`](/react-native/docs/textinput.html#content) is a basic component that allows the user to enter text.
+
+This example creates a simple `TextInput` box with the `string` `Hello` as the placeholder when the `TextInput` is empty.
+
+```JavaScript
+import React from 'react';
+import { AppRegistry, TextInput, View } from 'react-native';
+
+const App = () => {
+  return (
+      <View>
+        <TextInput placeholder="Hello" />
+      </View>
+  );
+}
+
+// App registration and rendering
+AppRegistry.registerComponent('MyApp', () => App);
+```