fix: add hover effect on scrollToTop-btn

[RohitKS7]

I added a hover effect on the scroll-to-top button for hover supporting devices.

Fixes Issue

closes #1394

Changes proposed

Check List (Check all the applicable boxes)

• [x] My code follows the code style of this project.
• [x] My change requires changes to the documentation.
• [x] I have updated the documentation accordingly.
• [x] All new and existing tests passed.
• [x] This PR does not contain plagiarized content.
• [x] The title of my pull request is a short description of the requested changes.

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Note to reviewers