Mention IDNs explicitly in site name algorithm

[aphillips]

4.1.4 Site names
https://www.w3.org/TR/2026/WD-attribution-20260602/#site-name-algorithm

These sites MUST all be in scheme-and-host form, with a scheme of "https". This means that a simple string serialization of a host is sufficient to identify the site. The API is therefore able to use a simple string to represent sites.

This section includes an algorithm for parsing the domain name and uses the URL spec's "obtain a registerable domain name" definition, so it supports IDNs (non-ASCII internationalized domain names). However, no mention is made of IDNs. The I18N WG thinks that mentioning the possibility of non-ASCII domain names in the "simple string" would guard against bad assumptions and help promote e.g. ICANN's Universal Acceptance goals.

Consider adding a mention such as:

The API is therefore able to use a simple string to represent sites. (Note that the name may be a non-ASCII IDN.)

[AramZS]

We see this feedback and will address it, thank you!