Updating "Slant & Italics" section, now that Recursive has Slant & Cursive axes (and no Italic)

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With Release 1.046/1.047 of Recursive, the family no longer accurately falls under the description of "Slant & Italics," largely because after several conversations with Dave Crossland and DJR, I've come to the conclusion that a font probably shouldn't contain both Slant & Italic axes – or at least, it didn't make sense for Recursive.

I wrote more about the issue in notes on the topic of Slant & Italic axes in Recursive.

The main thing: I updated the Italic axis to "Cursive," because ital 1 should result in the "Italic" style of a typeface. The axis I had didn't really do that – instead, it tweaks cursive letterform substitution behavior along the Slant axis.

I don't think I can totally rewrite this section in a way that everyone would be happy with (especially without chatting it over, first). However, a few things that I believe should change are:

• The slnt axis should be -15 to 0 (it is a negative range). It shouldn't be capped at 10 degrees. Also, it only gets positive numbers if it is being called from the declaration font-style: oblique XXdeg.
• ital should change to CRSV in this section
• CRSV should have a step of 0.5, so that its default "auto substitution" setting can be the default shown. This allows Cursive alternates to auto swap in at slnt -14. Setting CRSV to 0 prevents this (letters stay roman up to slnt -15, and setting CRSV to 1 asserts cursive alternates at any slant.
• I'm not sure if it's worth saying, but once browsers properly support font-style for variable fonts, the Slant axis will work quite well with this property – no font-variation-settings required unless people want to adjust the CRSV axis. Of course, this will take months (at minimum), so maybe it's fine to recommend font-variation-settings font now, and update later when font-style is better supported.

Of course, it's possible we should just remove this "Slant & Italics" section entirely, and (hopefully) move this slnt+CRSV example up to the "Slant" section. For one thing, "Slant & Italics" is under "Registered Axes," which is no longer true. Also, even DJR said that Roslindale Italic Variable Beta, in combining slnt+ital, doesn't do things in a way he would likely do them today (paraphrasing his words). So, this probably isn't a thing that we really need to be advocating for. Instead, we should try to help people understand when Slant is useful vs when Italic is better.

I've started a PR to update the site to Recursive 1.047, and start making a few of these basic changes:

https://github.com/jpamental/variable-fonts/pull/204

Next steps would be discussing what we do to update the content. Do we try to update a little bit, or a lot?