feat: add Executable insterface

Author: Abdalrhman Emad Saad

src/Engines/Contracts/Executable.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Kettasoft\Filterable\Engines\Contracts;
+
+use Illuminate\Database\Eloquent\Builder;
+
+interface Executable
+{
+  /**
+   * Execute using the given query builder instance.
+   * @param \Illuminate\Database\Eloquent\Builder $builder
+   * @return \Illuminate\Database\Eloquent\Builder
+   */
+  public function execute(Builder $builder);
+}