add mock request to docs

litellm/tests/test_mock_request.py

@@ -0,0 +1,21 @@
+#### What this tests ####
+#    This tests mock request calls to litellm 
+
+import sys, os
+import traceback
+
+sys.path.insert(
+    0, os.path.abspath("../..")
+)  # Adds the parent directory to the system path
+import litellm
+
+def test_mock_request():
+    try:
+        model = "gpt-3.5-turbo"
+        messages = [{"role": "user", "content": "Hey, I'm a mock request"}]
+        response = litellm.completion(model=model, messages=messages, mock_request=True)
+        print(response)
+    except:
+        traceback.print_exc()
+
+test_mock_request()