Add Punycode support

[thekid]

This is what the JavaScript URL class does:

[thekid]

We could port https://metacpan.org/pod/Net::IDN::Encode, bundle https://packagist.org/packages/rowbot/idna (MIT license) or revive https://github.com/xp-framework/core/blob/61726dfb62d6ba512a1a0a1fa0799eb3a7c75d4d/skeleton/org/ietf/PunyCode.class.php