Generate dark variants for ringOpacity by default

Author: adamwathan

stubs/defaultConfig.stub.js

@@ -822,7 +822,7 @@ module.exports = {
     ringColor: ['responsive', 'dark', 'focus-within', 'focus'],
     ringOffsetColor: ['responsive', 'dark', 'focus-within', 'focus'],
     ringOffsetWidth: ['responsive', 'focus-within', 'focus'],
-    ringOpacity: ['responsive', 'focus-within', 'focus'],
+    ringOpacity: ['responsive', 'dark', 'focus-within', 'focus'],
     ringWidth: ['responsive', 'focus-within', 'focus'],
     rotate: ['responsive', 'hover', 'focus'],
     scale: ['responsive', 'hover', 'focus'],