docs: update README for MongoDB server version compat (#1293)

README.md

@@ -20,6 +20,14 @@ npm start
 ```
 This will run Goof locally, using a local mongo on the default port and listening on port 3001 (http://localhost:3001)
 
+Note: You *have* to use an old version of MongoDB version due to some of these old libraries' database server APIs. MongoDB 3 is known to work ok.
+
+You can also run the MongoDB server individually via Docker, such as:
+
+```sh
+docker run --rm -p 27017:27017 mongo:3
+```
+
 ## Running with docker-compose
 ```bash
 docker-compose up --build