Strict regex performance issue

pre: #290 https://github.com/mvdan/xurls/blob/ee9499d3fc7b6557f435e241350b262c5d1ded82/xurls.go#L145 I found that `xurl.Strict()` trying to match various schemes, the schemes list is so long that we saw very huge performance downgreade with --strict-regex enabled.