Public Sans - Feature: [add support for pinyin with tones]

[vivvienne]

Is your feature request related to a problem? Please describe.

Hi.

While I was using the font with some text including pinyin with tones, I noticed some characters are not currently supported. So I did a simple check with a table for letters used in pinyin at Wikipedia, and found that these single codepoint characters seem to be absent in Public Sans.

• Ǎ, Ǐ, Ǒ, Ǔ, ǎ, ǐ, ǒ
• Ǖ, Ǘ, Ǚ, Ǜ, ǖ, ǘ, ǚ, ǜ
• (rare letters) Ḿ, Ǹ, ḿ, ǹ

While the ones in the 1st and 3rd rows (with only 1 diacritic) can still be expressed with the base letter and a combining diacritic (such as a combining caron U+030C), the ones in the second row (with a diaeresis and another diacritic) cannot be done so because the positions of combining diacritics clash with one another.

Other rarer combinations also suffer from the diacritic clashing problem: Ê̄, Ê̌, ê̄, ê̌.

And other combinations seem for some reason to not combine at all: M̄, M̌, M̀, m̄, m̌, m̀.

Describe the solution you'd like

It would be great if

• Single codepoint characters exist in the font as precomposed characters
• Composed characters using combining diacritics do combine without clashing

Describe alternatives you've considered

No response

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct.
• I checked the current issues for duplicate feature requests.