copy everything in one go and parse them in the destination directory; easier than parsing each file and figuring out where to save it

instead of npm ci

return an empty string immediately if the input value is falsy

fixes #1344

ensure backwards compatibility, so that both `embed` and `data-embed` attributes can be used to not inline a style tag

css.purge should run after posthtml-mso, so that it can actually remove outlook comments

it should preserve selectors used for email client targeting

get parser directives working again

no-widows is just shorter to write than prevent-widows