Create "stub" file for IDE completion

Author: jasonmccreary

.stub.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace Illuminate\Testing {
+    class TestResponse
+    {
+        /**
+         * Assert that the response view has a given piece
+         * of bound data and its value is `null`.
+         */
+        public function assertViewHasNull(string $key): static {}
+    }
+}