[Documentation] Hetrodyne detection

[jomosh]

One of blah2 use-cases is to operate as a hetrodyne detector.

• This ticket is to document the steps required to operate blah2 as a detector. The scenario is as follows:

1. Target is a radio in RX mode listening to frequency X (best to choose not well used frequency to demonstrate this point)
2. Target starts to receive RF traffic (or we can illuminate target)
3. Target's LO produces RF noise
4. blah2 detects signal reflection
5. Can we also utilise 3lips (with multiple radios) for direction and range finding?

I'm happy to work on the documentation of this use-case.