Update app.py

Documentation update in Numpydoc style.

app.py

@@ -68,7 +68,23 @@ I request that the following data is removed from The Stack and StackOverflow:
 _Note_: If you don't want all resources to be included just remove the elements from the list above. If you would like to exclude all repositories and resources just add a single element "all" to the list.
 """
 
-def issue_url(username, repos):
+def issue_url(username:str, repos:list):
+    """
+    Generate the URL for creating an issue related to opting out from The Stack.
+
+    Parameters
+    ----------
+    username : str
+        The username for which the issue is being created.
+    
+    repos : list of str
+        The list of repositories associated with the username.
+
+    Returns
+    -------
+    str
+        The URL for creating the opt-out issue.
+    """
     title = urllib.parse.quote(opt_out_issue_title.format(username=username))  
     body = urllib.parse.quote(opt_out_issue_body.format(repo_list=" - "+ "\n - ".join(repos)))
     
@@ -76,7 +92,23 @@ def issue_url(username, repos):
     
     return opt_out_text
 
-def check_username(username, version):
+def check_username(username:str, version:str):
+    """
+    Check if the username has code in The Stack for a specific version.
+
+    Parameters
+    ----------
+    username : str
+        The username to check.
+    
+    version : str
+        The version to check.
+
+    Returns
+    -------
+    tuple of str
+        A tuple containing the result markdown and the opt-out issue URL.
+    """
     output_md = ""
     repos = []
     if username in usernames: