Add Group, Limit, Map, Sort functions

Signed-off-by: davidarendsen <davidarendsen@hey.com>

src/Function/Map.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Arendsen\FluxQueryBuilder\Function;
+
+class Map extends Base {
+
+    /**
+     * @var array $query
+     */
+    private $query;
+
+    public function __construct(string $query)
+    {
+        $this->query = $query;
+    }
+
+    public function __toString()
+    {
+        return '|> map(fn: (r) => ({ ' . $this->query . ' })) ';
+    }
+
+}