minifyHTML may not wrap attributes with double quotation

[yw662]

> minifier.minifyHTML(`<div style="background: red"></div>`)
'<div style="background: red"></div>'

This is valid, but the space is not trimmed.

> minifier.minifyHTML(`<div style="background:red"></div>`)
"<div style=background:red></div>"

However this is invalid HTML without double quotation, which is a bug that should be fixed.