Add form label description docs and example
Closes #936
Relates to #897
Context
Follow-up docs issue to gitlab-org/gitlab-ui!2220 (merged). We add docs and example for label descriptions to the form group component.
Screenshot
Edited by -
Closes #936
Relates to #897
Follow-up docs issue to gitlab-org/gitlab-ui!2220 (merged). We add docs and example for label descriptions to the form group component.