docs(contributing): explain labels and milestones
docs(contributing): explain labels and milestones

AyogoHealth/router,excellalabs/router,excellalabs/router,loomio/router,JanPietrzyk/router,AyogoHealth/router,kyroskoh/router,shangyilim/router,IgorMinar/router,rakeshbhavsar/router,angular/router,JanPietrzyk/router,IgorMinar/router,kyroskoh/router,loomio/router,IgorMinar/router,rakeshbhavsar/router,shangyilim/router,shangyilim/router