Pick styles from clipboard data transfer when pasting from Word

[Marek Lewandowski]

While serializing to HTML Word inlines styles to some elements, while leaving classes in others.

A style element that contains all the styles for given selector is put in html > head element of text/html clipboard which is currently not pasted into CKEditor.

What we need to do here is to make sure that we check text/html dataTransfer for these style elements, and inline them into matched elements.

One thing to keep in mind that we don't want to inline mso- specific styles. At the end it's fine for us to inline even unknown css, as those will be stripped by ACF.