Update the HTML boolean attributes per the HTML 5.1 spec

- Add attributes `allowfullscreen`, `default`, `inert`, `sortable`,
`truespeed`, `typemustmatch`.
- Fix attribute `seamless` (previously misspelled `seemless`).
- Use `assert_dom_equal` instead of `assert_equal` in test.
Merge pull request #10949 from alexpeattie/update_html_boolean_attrs

Update HTML boolean attributes per the HTML 5.1 spec