feat(GlFormFields): Add validator for emojis

mentioned in commit 70d7f99e

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!186 (merged)

mentioned in merge request status-page!851 (merged)

mentioned in merge request gitlab!128113 (closed)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3432 (merged)

mentioned in merge request gitlab-docs!4162 (merged)

mentioned in merge request gitlab!126562 (merged)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!197 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3508 (merged)