feat(GlSparklineChart): Add `connectNulls` prop

mentioned in commit af886746

mentioned in merge request status-page!903

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!338 (merged)

mentioned in merge request gitlab!159500 (merged)

mentioned in merge request gitlab!159601 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3956 (merged)

mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!726 (closed)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!43 (merged)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!45 (merged)

mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!783 (closed)

mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!811 (closed)