Add license texts for two more test fonts

[musicinmybrain]

Since chromacheck-colr.ttf is derived from

https://github.com/RoelN/ChromaCheck/raw/d2b0f87bf3e88e1a443d7fceec68ff6eb331df1e/fonts/chromacheck-colr.woff

its license (MIT) is

https://github.com/RoelN/ChromaCheck/raw/d2b0f87bf3e88e1a443d7fceec68ff6eb331df1e/LICENSE.md

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Add license text for STIXTwoMath-Regular.ttf

https://github.com/stipub/stixfonts/raw/refs/tags/v2.13/AUTHORS.txt
https://github.com/stipub/stixfonts/raw/refs/tags/v2.13/OFL.txt

[musicinmybrain]

I still wasn’t able to definitively identify the correct license for tests/data/SparseFont.ttf, which was introduced in #84.

I also wasn’t able to definitively identify the correct license for tests/data/noto_handwriting-cff2_colr_1.otf and tests/data/test_glyphs-glyf_colr_1.ttf, which were introduced in 5a80c3e by copying them from harfbuzz, where they were introduced in harfbuzz/harfbuzz@30a6fd0. That commit didn’t help me understand exactly where they came from, so I couldn’t be 100% certain what their licenses were.