[DOCS] make an explicit warning not to create clients for each request

doc/contributors.rst

@@ -18,3 +18,4 @@ The following is a list of people who have contributed to
 - Steven Silvester
 - Julius Park
 - Doeke Buursma
+- Scott Luu

doc/tutorial-asyncio.rst

@@ -454,11 +454,10 @@ to an :class:`aiohttp.web.Application`:
   :start-after: main-start
   :end-before: main-end
 
-Note that it is a common mistake to create a new client object for every
-request; this comes at a dire performance cost. Create the client
-when your application starts and reuse that one client for the lifetime
-of the process. You can maintain the client by storing a database handle
-from the client on your application object, as shown in this example.
+.. DANGER::
+   It is a common mistake to create a new client object for every request; this comes at a dire performance cost. 
+   Create the client when your application starts and reuse that one client for the lifetime of the process.
+   You can maintain the client by storing a database handle from the client on your application object, as shown in this example.
 
 Visit ``localhost:8080/pages/page-one`` and the server responds "Hello!".
 At ``localhost:8080/pages/page-two`` it responds "Goodbye." At other URLs it