This diff introduces the new color design system/light mode to the sidebar promote modal
For additional context about this new color design system and the new naming convention here is the notion doc:
https://www.notion.so/commapp/New-Color-System-Proposal-ef80b4e4b9ec42949095056161223a42
Linear task: https://linear.app/comm/issue/ENG-5038/sidebar-promote-modal
Depends on D10572