readme: add additional info about checkAnnotation values
readme: add additional info about checkAnnotation values

jscs-dev/jscs-jsdoc,shaoshing/jscs-jsdoc,MunGell/jscs-jsdoc,lvivier/jscs-jsdoc,szarouski/jscs-jsdoc,dtracers/jscs-jsdoc,jdlrobson/jscs-jsdoc