[Contributing] Added class coding standards

CONTRIBUTING.md

@@ -8,6 +8,22 @@ It's dead simple, use the issue tracker. Be descriptive, remember this is a comm
 
 Please follow existing coding standards:
 
+```php
+<?php
+
+namespace Foo\Bar\Controller;
+
+use Foo\Bar\Bar;
+
+class Foo extends Bar {
+    public function baz() {
+        if ($condition) {
+        }
+    }
+}
+```
+
+- Atleast one newline seperating `namespace`, `use`, and `class` declarations
 - Spaces around operators and control blocks:
     ```php
     if ($condition) {