docs: Update AddPlatform and Web screenshots, fix step 6 text

Updated AddPlatform.png and Web.png with latest Azure portal UI.
Updated step 6 from 'Add a platform' to 'Add redirect URI' in create_new_app_registration.md.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Thanusree-Microsoft

documents/Images/AddPlatform.png

@@ -20,7 +20,7 @@
 
 ![Redirect URL](Images/AddRedirectURL.png)
 
-6. Click on `+ Add a platform`.
+6. Click on `+ Add redirect URI`.
 
 ![+ Add platform](Images/AddPlatform.png)