added smooth scroll to back to top button

[Niyatizzz]

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  /kind feature
  /kind cleanup
  /kind design

• What this PR does / why we need it:
  Enables smooth scrolling to the top of the page when "Back to Top" is clicked along with a neat tooltip.

• Which issue(s) this PR fixes:
  fixes "Back to Top" scroll can be made into a smooth transition #388

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[Niyatizzz]

/assign @Thor-wl @Monokaix
/assign @k82cn

hii there, please review the pr and let me know if any changes are required
thanks!