Add addBottom function

Signed-off-by: David Arendsen <darendsen@gamepoint.com>

src/Functions/Bottom.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Arendsen\FluxQueryBuilder\Functions;
+
+use Arendsen\FluxQueryBuilder\Type\ArrayType;
+
+class Bottom extends Base
+{
+    /**
+     * @var int $n
+     */
+    private $n;
+
+    /**
+     * @var array $columns
+     */
+    private $columns;
+
+    public function __construct($n, array $columns = [])
+    {
+        $this->n = $n;
+        $this->columns = $columns;
+    }
+
+    public function __toString()
+    {
+        $input = new ArrayType(array_filter([
+            'n' => $this->n,
+            'columns' => $this->columns ?: null,
+        ]));
+        return '|> bottom(' . $input . ') ';
+    }
+}