[refactor] Lift the theme contract out of the Tailwind config - #5740

1 935 tests  ±0   1 924 ✅ ±0   20s ⏱️ -5s
    1 suites ±0      11 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit d9a1dc1. ± Comparison against earlier commit b7a5916.