Add jQuery in jest test_setup

What does this MR do?

This MR exposes jQuery to the global window object in Jest's test_setup. This greatly simplifies the migration to Jest. After we've migrated our karma scripts to Jest, then we should consider improving this. https://gitlab.com/gitlab-org/gitlab-ee/issues/12448

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content