add mm list/download to docs
add mm list/download to docs

nvbn/Unofficial-Google-Music-API,dvirtz/gmusicapi,tanhaiwang/gmusicapi,simon-weber/Unofficial-Google-Music-API,peetahzee/Unofficial-Google-Music-API,TheOpenDevProject/gmusicapi,thebigmunch/gmusicapi,jimyx17/gmusic,simon-weber/gmusicapi,dvirtz/gmusicapi