Add enter keyboard shortcut to submit Related Issues form

What does this MR do?

Add enter keyboard shortcut to submit Related Issues form

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

Why was this MR needed?

Add the native form submission feel

Does this MR meet the acceptance criteria?

• 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 #2925 (closed)