[whatwg] Allow omitting ="" for attributes?

[Rohan Prabhu]

In that case, we need to have a provision in either DTD or XML-Schema
to allow empty attributes and take default values instead, as this
proposal clearly violates XML Syntax rules.

And we need to have a DTD, Schema or a validation entity somewhere to
materialize the WHATWG's specifications.

Rohan Prabhu