Add wp functions

[MAILPOET-2639]

lib/WP/Functions.php

@@ -574,6 +574,22 @@ class Functions {
     return plugins_api($action, $args);
   }
 
+  /**
+   * @param int|string|array $post Optional. Post ID, title, slug, or array of such. Default empty.
+   * @return bool Whether the query is for an existing single post.
+   */
+  public function isSingle($post = '') {
+    return is_single($post);
+  }
+
+  /**
+   * @param int|string|array $page Optional. Page ID, title, slug, or array of such. Default empty.
+   * @return bool Whether the query is for an existing single page.
+   */
+  public function isPage($page = '') {
+    return is_page($page);
+  }
+
   /**
    * @param string $package
    * @param array $args