Mention to load module-raop-discover on website

[UlrikBuchholtz]

First of all, thanks for making and maintaining this, and thanks for your efforts to get this into the mainline pulseaudio! I'm using it to stream to a Philips Fidelio AD7000W with no problems.

But I think the website could mention in Section 4 that it's necessary to load the module-raop-discover module via

./src/pactl load-module module-raop-discover

or else to add load-module module-raop-discover to src/default.pa.

[hfujita]

Thank you for being a user of the raop2 patch, and thank you for your suggestion.
Actually, the "paprefs" section in the section 3 does enable module-raop-discover. If you think it'd be good to have a tip for non-GUI users, I'm happy to take a pull request.