Resolve "Don't lose user content in wiki"

What does this MR do?

It prevents closing/leaving the Wiki Edit page if user has a draft in the comment form. Now, when user intends to leave the page, they will see the warning about unsaved changes

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Issue: #213652 (closed)