Add subfeatures to indicate support for CSS typed arithmetic

[chrisdavidmills]

Summary

Chrome 140 adds support for CSS typed arithmetic; see https://chromestatus.com/feature/4740780497043456.

It is not very clear what this is from the spec, but https://css-tricks.com/css-typed-arithmetic/ provides a good explanation.

Safari also supports it. The relevant bug appears to be https://bugs.webkit.org/show_bug.cgi?id=278244, which says Safari 18, but I've tried 18.5 and it doesn't work in that version. I upgraded to Safari 26, and it did work, so I've put the Safari support version down as 26.

In terms of what features this will be used in, it is mainly relevant to calc(). abs() and sign() also directly take a calculation/expression as a value, and I've tested it works on them, so I've included the data point on those functions as well.

In terms of including it in other function data, I don't know. I mean, you can technically use a calc() just about anywhere that accepts numeric units, but I didn't think it was worth including it in other places as it would get confusing. Opinions welcome.

Test results and supporting details

Related issues

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