Improve documentation on "Test from other devices"

[tonyhallett]

The documentation should mention that you should get the address of your local machine and providing that when you connect to the emulator in code.
e.g https://firebase.google.com/docs/reference/js/database.md#connectdatabaseemulator_27b9e93

This medium article filled in the gaps.

[aalej]

Hey @tonyhallett, thank you for the feedback. I agree that a clearer documentation on how to connect to the Firebase emulator from a physical device would be a good improvement.

I think it would be helpful if it was added here https://firebase.google.com/docs/emulator-suite/connect_rtdb#web, and mentioned that when testing using a physical device, the address of the machine running the Firebase emulator should be used as the host address.