Refine leaderboard toggles with square styling and polished hover glow (#6)

* updating landing page leaderboard styling and polishing mobile view

* updating leaderboard pills to be rounded

* updating leaderboard pill selectors

* Update client/src/components/Leaderboard.jsx

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update client/src/components/Leaderboard.jsx

Author: Ammaar-Alam