fix: add missing self parameter to static_handler method in Application class

src/snek/app.py

@@ -254,7 +254,7 @@ class Application(BaseApplication):
         return rendered
 
 
-    async def static_handler(request):
+    async def static_handler(self, request):
         file_name = request.match_info.get('filename', '')
 
         paths = []