refactor: onboarding notice

[Soare-Robert-Daniel]

Summary

Make the onboarding notice similar to the one in Raft and screenshot on the issue.

Will affect visual aspect of the product

YES

Screenshots

Test instructions

• Install Neve in a fresh instance
• Check if the button works
• Check if the layout is ok

Check before Pull Request is ready:

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

Closes https://github.com/Codeinwp/neve-pro-addon/issues/2909

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