adds readme and corect rule configuration

Author: selul

README.md

@@ -1,3 +1,19 @@
 # Themeisle ruleset 
 
 Global phpcs ruleset 
+
+
+###Usage
+
+Install it using 
+`composer require codeinwp/phpcs-ruleset --dev`
+
+Add in your project phpcs.xml configuration file: 
+
+```xml
+<?xml version="1.0"?>
+<ruleset>
+    <file>.</file>
+    <rule ref="Themeisle"/>
+</ruleset>
+```