The itemtype attribute is a space-separated list

[da2x]

The itemtype attribute accepts a space-separated list of URLs.
https://html.spec.whatwg.org/#attr-itemtype

Tidy incorrectly merges space-separated itemtype values into one value and URL-encodes the separator whitespace.

E.g.

<div itemtype="https://schema.org/Organization https://schema.org/WebSite">

turns into

<div itemtype="https://schema.org/Organization%20https://schema.org/WebSite">

This patch changes CH_URL to CH_PCDATA. (CH_RDFATERMS, used on the RDFa-equivalent typeof attribute, is the closest datatype, but it expects prefixes and not URLS. CH_URLS is the most similar data type, but it also allows comma-separated lists, which isn’t appropriate here. Switching to CH_PCDATA is better than leaving it broken.)