Add a tooltip to Add Designs button

What does this MR do?

A tooltip should be added to the Add Designs button that informs the user about the replacement of the design if it has the same file name as already uploaded one.

Text: Adding a design with the same filename replaces the file in a new version.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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