explain the unbridge feature in README.md
**Is your feature request related to a problem? Please describe:**
I was digging though the code and the issues here to find out what code the HomeKit App on iOS is asking for to configure the camera manually.

**Describe the solution you'd like:**
I would love to have a step by step guide (I'd write it though) how to add an unbridged camera to HomeKit

**Describe alternatives you've considered:**
obvioulsy it is the config code of the homebridge instance, but nonetheless, it is not as straight forward as I thought

**Additional context:**
iOS 14.6

