Add "auto" to axes that interact with other axes

[davelab6]

In discussing the axis registration protocol with @vv-monsalve today, we compared the Cursive and Wonky axes

• https://fonts.google.com/knowledge/glossary/wonky_axis
• https://github.com/googlefonts/axisregistry/blob/main/Lib/axisregistry/data/wonky.textproto
• https://fonts.google.com/knowledge/glossary/cursive_axis
• https://github.com/googlefonts/axisregistry/blob/main/Lib/axisregistry/data/cursive.textproto

@thundernixon invented this nice 'auto' 0.5 value in the Cursive axis of Recursive, which controls the cursive glyph substition along the Slant axis, allows users to get cursive forms at the max slant, or turn them on manually sooner, even with slant 0 (min), or, keep them off at slant max.

@sponcey and @flaviazim and @arialcrime set up the Wonky axis in Fraunces in a similar way, where the Optical Size axis will show Wonky glyphs at large sizes (22+) and normal glyphs at smaller sizes, and the Wonky axis can manually obtain NonWonky glyphs at large sizes:

However this doesn't work for small sizes to turn Wonky on; arguably this is correct as Wonky isn't useful at small sizes and interferes in readability:

So, we wonder about updating the axis definition and the Fraunces project be updated to support an Auto value, next time the project advances to fix all other known bugs. This will be useful to inform the next project that uses the Wonky axis, whatever that is :)

[RosaWagner]

Would this also apply to VOLUME which is interacting with FLAIR?

[vv-monsalve]

Cursive is a boolean (pseudo) axis that controls the substitution of glyphs to cursive forms, with that third "auto" position enabled. Wonky is currently a boolean axis that could be improved to include this same auto position.

Since Volume is a continuous range axis, and we are no longer including fallbacks per axis definition I don't see how it could be ruled per axis basis to be used in that way. Perhaps is something that could be enabled per font basis (STAT format 4. as I think Commissioner is already doing)

@davelab6?