Add solution info about `ModuleNotFoundError: No module named 'google'` error

Adding-Steam-to-Aegis-using-the-'steam'-Python-library.md

@@ -67,6 +67,24 @@ sa.status() # Optional. Output should look something like below if everything wo
 
 exit() # You're done!
 ```
+
+## Troubleshooting
+
+- Issue: `from steam.guard import SteamAuthenticator` fails with the following error:
+
+  ```
+  >>> from steam.guard import SteamAuthenticator
+  Traceback (most recent call last):
+    File "<stdin>", line 1, in <module>
+    File "python/3.9.12/lib/python3.9/site-packages/steam/guard.py", line 61, in <module>
+      from steam.utils.proto import proto_to_dict
+    File "python/3.9.12/lib/python3.9/site-packages/steam/utils/proto.py", line 4, in <module>
+      from google.protobuf.message import Message as _ProtoMessageType
+  ModuleNotFoundError: No module named 'google'
+  ```
+
+  Solution: install the [google-api-python-client](https://pypi.org/project/google-api-python-client/) package with `pip install --upgrade google-api-python-client`.
+
 ## Questions
 
 Q: Something went wrong! What do I do?