required attribute is not supported for validation

Phenomenon

The required attribute, which works on form inputs to indicate mandatory fields, is not supported on contenteditable regions. There is no built-in way to mark a contenteditable as required for form validation.

Reproduction example

1. Create a contenteditable div with required attribute inside a form.
2. Try to submit the form without entering content.
3. Observe whether validation occurs.

Observed behavior

• In Chrome on macOS, the required attribute is ignored on contenteditable.
• Form validation does not check contenteditable regions.
• No built-in validation exists.

Expected behavior

• The required attribute should work on contenteditable.
• Form validation should check contenteditable regions.
• Or, there should be a standard way to validate contenteditable content.