The HTML writer adds the `data-` prefix for HTML5 for nonstandard attributes. But the attributes are represented in the AST without the `data-` prefix, so we should strip this when reading HTML. Closes #5392.
The HTML writer adds the `data-` prefix for HTML5 for nonstandard attributes. But the attributes are represented in the AST without the `data-` prefix, so we should strip this when reading HTML. Closes #5392.