feat(GlAccordion): add chevron animation

mentioned in commit 8d18e603

mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!1298 (merged)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!55 (closed)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!352 (merged)

mentioned in merge request status-page!903

mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!1299 (closed)

mentioned in merge request gitlab!171760 (closed)

mentioned in merge request gitlab!173736 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!4186 (merged)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!58 (merged)