WIP: Issue title vue realtime update

What does this MR do?

Here is the relevant issue: #25051 (closed)

This MR begins the work needed to update the title on issue:show pages.

Currently using Vue in anticipation of expansion of scope.

Uses ruby provided title on page load, and then makes async calls to update the title every 3 seconds (only for logged-in users).

Calls stop when page is out of focus and reloaded to avoid turbolinks caching the API and having users send too many calls while the tab is open and out of focus.

CSS animations are taken care of.

This MR is blocked by #26396 (closed) which is very important for the future of GitLab and realtime

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

#25051 (closed)

#26396 (closed)