Add a migration tip for .label to .label-default
Add a migration tip for .label to .label-default

BS3 commits: 7b945ad29641444133f3fb8db2b8f3e94332c3f1

aaroncnhk/todc-bootstrap,mozillo/todc-bootstrap,todc/todc-bootstrap,todc/todc-bootstrap,ztx1491/todc-bootstrap,todc/todc-bootstrap,2947721120/todc-bootstrap,2947721120/googlebt4,up2vs/todc-bootstrap