Allow Building without mp3 support

Is your feature request related to a problem? Please describe. Installing the libmp3lame dependency on macOS looks annoying, and I don't plan on using the mp3 feature anyway, so it'd be nice to not include it in the build process.

Describe the solution you'd like An option to build without mp3 conversion support, excluding mp3lame

Yeah brew install lame doesn't seem to actually install the library on mac and there's not a ton of info online.

btw, I was able to compile it in the end by just deleting all the mp3-related code. But I was in a rush so I didn't try to implement it as an actual feature

I ended up just building it in a docker container and bypassed running it directly on the Mac OS. That said, I'd support a build that doesn't require that dependancy (I'm using it with Traktor which can read ogg so I'd rather not reencode anyways)

The library is only required for linking. Include the path here.

export LIBRARY_PATH="/usr/local/lib"
ln /opt/homebrew/opt/lame/lib/libmp3lame.dylib "$LIBRARY_PATH/libmp3lame.dylib"