chore: clarify how connect peers to a same meeting

[Mazuh]

Description of changes:

Just added a clarification to this readme about connecting peers.

I was trying to create a simple app using Chime SDK and failed for days because I didn't notice I was not using meeting ids correctly as I had a different expectation of how they would work based on previous WebRTC tools that I used in the past.

Checklist:

1. Have you successfully run npm run build:release locally? Nope, no code changes.

2. Do you add, modify, or delete public API definitions? If yes, has that been reviewed and approved? No.

3. Do you change the wire protocol, e.g. the request method? If yes, has that been reviewed and approved? No.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.