Fix handling of astral character reference

[Porges]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)
• If applicable, I’ve added docs and tests

Description of changes

decodeNumericCharacterReference was using String.fromCharCode which only handles UTF-16 code units, not true codepoints. Any characters not representable by a single UTF-16 code unit ("astral characters") would come out incorrectly.

Note that there are other uses of String.fromCharCode in micromark. These should also be examined. The current behaviour is a regression that was introduced 4 months ago by bbb726d, although the correct version only existed for 3 days prior to that 🙂 — the very first version of the function had the same problem.

[codecov-commenter]

Codecov Report

Merging #158 (21a77fc) into main (e0dce3d) will not change coverage.
The diff coverage is 100.00%.

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@@            Coverage Diff            @@
##              main      #158   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           57        57           
  Lines        11936     11936           
=========================================
  Hits         11936     11936           

Files	Coverage Δ
...il-decode-numeric-character-reference/dev/index.js	100.00% <100.00%> (ø)

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[wooorm]

Thanks!

[wooorm]

Our linter xo thought it was useful. But we mostly index into strings, so changing to code points actually breaks things. In this case it doesn’t though!

[wooorm]

Thank you, released! https://github.com/micromark/micromark/releases/tag/micromark-util-decode-numeric-character-reference%402.0.1

[Porges]

Thank you, released! https://github.com/micromark/micromark/releases/tag/micromark-util-decode-numeric-character-reference%402.0.1

Thanks for the quick turnaround 🙂