Add UX debt label to the contribution guidelines
Add UX debt label to the contribution guidelines

gitlab-design#29

iiet/iiet-git,axilleas/gitlabhq,jirutka/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,dreampet/gitlab,iiet/iiet-git,jirutka/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,dreampet/gitlab,jirutka/gitlabhq,iiet/iiet-git,t-zuehlsdorff/gitlabhq,stoplightio/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,axilleas/gitlabhq,t-zuehlsdorff/gitlabhq,stoplightio/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,axilleas/gitlabhq,jirutka/gitlabhq,mmkassem/gitlabhq,t-zuehlsdorff/gitlabhq,t-zuehlsdorff/gitlabhq