The original specification did not explicitly accept a URL object as an
input, and expected implicit conversion from the URL object to the
URLPatternInit object for matching.

This change make the URL object accepted as an input explicitly.
This is a step to fix whatwg#218.

- Not chagne `exec()` or `test()` arguments.
- make the match algorithm accept [=/url=].
- By merging existing steps, omitted the explicit declaration of
  anchors.

Co-authored-by: Domenic Denicola <d@domenic.me>

Co-authored-by: Jeremy Roman <jeremy@jeremyroman.com>