Diacritics are positioned incorrectly relative to double diacritics

[dscorbett]

Iosevka 7.0.0 does not support diacritics applied to double diacritics. This is a regression from #596. I recommend implementing it the way Noto Sans does, which is dead simple. This should work not just with CGJ but with any non-reordering default ignorable code point.

Here is <U+0169, U+0361, U+034F, U+030E, U+0069, U+030A, U+0169, U+035F, U+034F, U+0348, U+0069, U+030A>.

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• Your font version: 7.0.0
• Your font variant: Iosevka Slab Extended
• Your operating system (name and version): macOS 10.14.6
• Your application using Iosevka: hb-view