fix(github): unthemed elements

[thismoon]

🔧 What does this fix? 🔧

theme the bottom border of the selected navigation bar item with the accent color at /explore (and topic pages etc)

theme the --rgh-heat-color variable (which is used by refined github to highlight recent commits and most downloaded releases) with the peach color

🗒 Checklist 🗒

• I have read and followed Catppuccin's contributing guidelines.
• I have updated the version appropriately in the ==UserStyle== header of the catppuccin.user.css file.

[uncenter]

Thanks!