Update the import statements for the cookbook snippets (#1805)

Updates the import statements on
https://connexion.readthedocs.io/en/stable/cookbook.html


A few of the import statements were missing, or didn't match the example
code because they imported at the wrong depth.
This should make the code in the cookbook copy-pasteable.

---------

Co-authored-by: Robbe Sneyders <robbe.sneyders@gmail.com>

docs/cookbook.rst

@@ -17,12 +17,14 @@ Starlette. You can add it to your application, ideally in front of the ``Routing
 
         .. code-block:: python
         
+            from pathlib import Path
+
             from connexion import AsyncApp
             from connexion.middleware import MiddlewarePosition
             from starlette.middleware.cors import CORSMiddleware
 
 
-            app = connexion.AsyncApp(__name__)
+            app = AsyncApp(__name__)
 
             app.add_middleware(
                 CORSMiddleware,
@@ -49,12 +51,14 @@ Starlette. You can add it to your application, ideally in front of the ``Routing
 
         .. code-block:: python
         
+            from pathlib import Path
+
             from connexion import FlaskApp
             from connexion.middleware import MiddlewarePosition
             from starlette.middleware.cors import CORSMiddleware
 
 
-            app = connexion.FlaskApp(__name__)
+            app = FlaskApp(__name__)
 
             app.add_middleware(
                 CORSMiddleware,
@@ -81,9 +85,11 @@ Starlette. You can add it to your application, ideally in front of the ``Routing
 
         .. code-block:: python
         
+            from pathlib import Path
+
             from asgi_framework import App
             from connexion import ConnexionMiddleware
-            from connexion.lifecycle import ConnexionRequest, ConnexionResponse
+            from starlette.middleware.cors import CORSMiddleware
 
             app = App(__name__)
             app = ConnexionMiddleware(app)