added short explanation for creating custom plugins
added short explanation for creating custom plugins

cesarandreu/angulartics,jung01080/angulartics,aheuermann/angulartics,samanbarghi/angulartics,chechoacosta/angulartics,Affirm/angulartics,dy2288/angulartics,haimlit/angulartics,WoodWing/angulartics,marcin-wosinek/angulartics,RocketBus/angulartics,nathankot/angulartics,chovy/angulartics,cristoferdomingues/angulartics,MrHash/angulartics,TallyFox/angulartics,iamakimmer/angulartics,hvvikram/angulartics,dr-axly/angulartics,trolleycrash/angulartics,loggi/angulartics,martijndejongh/angulartics,abhilashsajeev/angulartics,rodikal/angulartics,werk85/angulartics,sampov2/angulartics,judemat/angulartics,geordie--/angulartics,JonnyBGod/angulartics,angulartics/angulartics,hfreire/angulartics,deedubs/angulartics,instilled/angulartics,hekike/angulartics,RideAmigosCorp/angulartics,indiegogo/angulartics,TwineHealth/angulartics,mushkab/angulartics,Ignigena/angulartics,fouasnon/angulartics,tlekan/angulartics,Gahen/angulartics,cwill747/angulartics,dasmith/angulartics