Possibility of a FLEX decoder

[ghost]

Hi all, thanks for all your hard work on the Mayhem Firmware, I've been having a lot of fun with it.

I was wondering if it was possible to add a FLEX Decoder alongside the POCSAG decoder as I have several interesting FLEX signals in my area.

I lack any coding ability to try and implement this myself but I would be more than happy to test it, provide feedback and write up any documentation if needed.

I don't know if this helps at all but it is a feature implemented in Multimon-ng, I've added the link to the specific decoder below:

https://github.com/craigshelley/multimon-ng/blob/master/demod_flex.c

Thanks for reading and sorry if this is a big ask.

[ArjanOnwezen]

Duplicate of #318