html:

• add descriptions to all properties so we get nice hovers
• version can be const: 1.
• properties.name should be required
• can there be both values and valueSet?
• unnecessary attributes.anyOf, globalAttributes.anyOf and valueSets.anyOf
• globalAttributes.required and itemSet.required need to be next to the properties
• add default values and defaultSnippets for better code completion experience (as requested in Issues with html customData schema #67609)

css:

• version can be const: 1.
• simplify oneOf:[{enum with `"enum": ["standard", "experimental",...]``
• add pattern and patternErrorMessage to verify browsers
• use $ref to have avoid multiple definitions for definitions for browsers and status