Translate contributors page dates

What does this MR do?

• Introduce a createDateTimeFormat wrapper to create Intl.DateTimeFormat instances for current locale.
• Translate dates on contributors page.

Screenshots

Before	After

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Review
  • Has been reviewed by Frontend
• Internationalization required/considered

What are the relevant issue numbers?

closes https://gitlab.com/gitlab-org/gitlab-ce/issues/39283, https://gitlab.com/gitlab-org/gitlab-ce/issues/38592