Do not require pathname to start with '/'.
Do not require pathname to start with '/'.

Not all URL pathnames are required to have a leading `/`.  For example,
`data:foo` has a pathname without a `/` and `data:` is a valid URL with
an empty string pathname.  In order to support matching these kinds of
URLs we therefore drop the assumption that pathname defaults to `/`.

kenchris/urlpattern-polyfill,kenchris/urlpattern-polyfill,kenchris/urlpattern-polyfill