v5.0.0

Changelog

• Add normalized sections not already present from
  https://html.spec.whatwg.org/multipage/.
• Move unsorted rules into their respective sections.
• Update the summary style in all browsers.
• Remove ::placeholder styles due to a bug in Edge.
• More explicitly define font resets on form controls.
• Remove the optgroup normalization needed by the previous font reset.
• Update text-size-adjust documentation
 for IE on Windows Phone
• Update OS X reference to macOS
• Update the semver strategy.