Add enums for action and condition names

src/Enum/FilterAction.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Opdavies\GmailFilterBuilder\Enum;
+
+class FilterAction
+{
+    const ADD_CATEGORY = 'smartLabelToApply';
+    const ADD_LABEL = 'label';
+    const ALWAYS_MARK_AS_IMPORTANT = 'shouldAlwaysMarkAsImportant';
+    const ARCHIVE = 'shouldArchive';
+    const FORWARD_TO = 'forwardTo';
+    const MARK_AS_READ = 'markAsRead';
+    const MARK_AS_SPAM = 'shouldSpam';
+    const NEVER_MARK_AS_IMPORTANT = 'shouldNeverMarkAsImportant';
+    const NEVER_MARK_AS_SPAM = 'shouldNeverSpam';
+    const STAR = 'shouldStar';
+    const TRASH = 'shouldTrash';
+}