I personally have not seen anything that performs FM demodulation or any SDR-related packages yet (though I have not looked very hard).
Resources
You can use Julia’s package web page to start searching:
I find the search a bit difficult to use effectively.
You can also try “JuliaObserver”, which is a web scraper (I believe):
Contributing
I personally don’t think SDR-related algorithms would go under DSP. I was looking into starting a different group called “JuliaTelecom”. This is a tentative name, and a more inclusive one might be better. You might want to take a peek at the following thread: