docs(app): add docstring to get_dad_joke()

app.py

@@ -17,6 +17,19 @@ def greet(name: str) -> str:
     return "Hello " + name + "!!"
 
 def get_dad_joke():
+    """
+    Fetches a random dad joke from the icanhazdadjoke.com API.
+    The function makes an HTTP GET request to the icanhazdadjoke API
+    with appropriate headers to receive JSON response.
+    Returns:
+        str: A random dad joke if successful, otherwise returns an error message.
+            - Success: Returns the joke text
+            - Failure: Returns "Failed to retrieve a joke." if the API request fails
+            - No joke: Returns "No joke found." if the API response doesn't contain a joke
+    Requires:
+        requests: The requests library must be imported to make HTTP requests
+    """
+
     headers = {"Accept": "application/json"}
     response = requests.get("https://icanhazdadjoke.com/", headers=headers)
     if response.status_code == 200: