add the find method to the interface

Author: themsaid

src/Illuminate/Bus/BatchRepository.php

@@ -15,6 +15,14 @@ interface BatchRepository
      */
     public function get($limit, $before);
 
+    /**
+     * Retrieve information about an existing batch.
+     *
+     * @param  string  $batchId
+     * @return \Illuminate\Bus\Batch|null
+     */
+    public function find(string $batchId);
+
     /**
      * Store a new pending batch.
      *