Indicate closed issues and MRs visually

What does this MR do?

In issues, for referred issues/MRs, the link name to closed issues is stricken.

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

The works - this is my first foray into this codebase.

Why was this MR needed?

Usability/ease of use.

Screenshots (if relevant)

Description:

Discussion:

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?

Closes #1369 (closed). This is a port of the code in the closed MR !1087 (closed).