Add no-unused-style documentation

Author: Intellicode

docs/rules/no-unused-styles.md

@@ -1 +1,83 @@
 # Detect unused StyleSheet rules in React components
+When working on a component over a longer period of time, you could end up with unused StyleSheet rules that slipt in over time but are forgotten as you continue to improve your UX/UI design.
+
+The following patterns are considered warnings: 
+
+```
+const styles = StyleSheet.create({
+  text: {}
+});
+
+const Hello = React.createClass({
+  render: function() {
+    return <Text>Hello {this.props.name}</Text>;
+  }
+});
+```
+
+The following patterns are not considered warnings:
+```
+const styles = StyleSheet.create({
+  name: {}
+});
+
+const Hello = React.createClass({',
+  render: function() {
+    return <Text style={styles.name}>Hello {this.props.name}</Text>;
+  }
+});
+```
+The most common case.
+
+```
+const styles = StyleSheet.create({
+  text: {}
+});
+const Hello = React.createClass({
+  propTypes: {
+    textStyle: Text.propTypes.style
+  },
+  render: function() {
+    return <Text style={[styles.text, textStyle]}>Hello {this.props.name}</Text>;
+  }
+});
+```
+Style rules referenced in a Style array are marked as used.
+
+```
+const styles = StyleSheet.create({
+  name: {}
+});
+
+const Hello = React.createClass({',
+  render: function() {
+    return <Text textStyle={styles.name}>Hello {this.props.name}</Text>;
+  }
+});
+```
+Rules are also marked as used when they are used in tags that contain the word `style`.
+
+```
+const styles = StyleSheet.create({
+  name: {},
+  welcome: {}
+});
+const Hello = React.createClass({
+  render: function() {
+    return <Text style={styles.name}>Hello {this.props.name}</Text>;
+  }
+});
+const Welcome = React.createClass({
+  render: function() {
+    return <Text style={styles.welcome}>Welcome</Text>;
+  }
+});
+```
+Usage is tracked over multiple components in the same file.
+
+```
+const styles = StyleSheet.create({
+  text: {}
+});
+```
+There should be atleast one component, so centralized `StyleSheets` are not checked for unused rules.