Document how to properly handle modals with dynamic content height
Document how to properly handle modals with dynamic content height

BS3 commits: 769c27a19f4ce8d5d298cedc07905d5300022e24

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