Version 3.5.6

What's Changed

• Feature: Merge Insiders-exclusive features by @billz in #2152 (the big merge 🎉)
• Feature: Extended user theme customization support by @billz in #2144
• Bump browserslist from 4.16.6 to 4.28.8 by @dependabot[bot] in #2150
• Bump brace-expansion from 1.1.13 to 1.1.18 by @dependabot[bot] in #2145
• Bump immutable from 3.8.3 to 3.8.4 by @dependabot[bot] in #2153
• Update release version: 3.5.6 by @billz in #2155

Full Changelog: 3.5.5...3.5.6