feat: add gl-md-max-w-30p and gl-md-w-50p classes

mentioned in commit 551cf2b0

mentioned in merge request gitlab!65077 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2437 (merged)

mentioned in merge request status-page!318 (merged)

mentioned in merge request gitlab-docs!1959 (closed)

mentioned in merge request gitlab-docs!1968 (closed)