[CJK design frame] Add the possibility to set frames of different sizes based on script/writing system

[mrk-z]

In Japanese design, there is the need to set the design frame to different sizes for Kanji, Hiragana, and Katakana glyphs.

This is currently not possible in Fontra.

In order to support Japanese design in Fontra, this would be a quite essential feature.

[mrk-z]

Mentioned in #1851

Related to #1965

[mrk-z]

In Glyphs, it's possible to add customized parameters and type things like:

han: 92
hira: 90
kata: 88

And the frames of Kanji, Hiragana, Katakana are set to 92%, 90%, 88%, respectively.

[justvanrossum]

What if each script could have its own independent CJK frame settings?

Btw. this also relates to having script-specific (global) guidelines, which is likely a very useful thing, too (see for example #1963).

[mrk-z]

Yes I think that would work.