added stub for creating new extender class

stubs/anchor-extender.stub

@@ -0,0 +1,14 @@
+<?php
+namespace {{namespace}};
+
+use Illuminate\Contracts\Support\Htmlable;
+use Illuminate\Contracts\Support\Renderable;
+use Kanuni\LaravelBladeAnchor\Contracts\Extender;
+
+class {{class}} implements Extender
+{
+    public function __invoke(?array $variables): string|Htmlable|Renderable
+    {
+        return '<p>Extending a view ...</p>';
+    }
+}