Copy examples from example repo

Fixes #4

examples/filters.php

@@ -0,0 +1,15 @@
+<?php
+
+use Opdavies\GmailFilterBuilder\Filter;
+
+require_once __DIR__ . '/vendor/autoload.php';
+
+return [
+    Filter::create()
+        ->from('foo@example.com')
+        ->labelAndArchive('Example'),
+
+    Filter::create()
+        ->from('bar@example.com')
+        ->important(),
+];