core: add DhkemX25519HkdfSha256 test for browsers.

[dajiaji]

No description provided.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.29%. Comparing base (4d0e8b1) to head (01d8518).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #550      +/-   ##
==========================================
+ Coverage   85.11%   85.29%   +0.17%     
==========================================
  Files          67       67              
  Lines        5678     5678              
  Branches      582      582              
==========================================
+ Hits         4833     4843      +10     
+ Misses        841      831      -10     
  Partials        4        4              

Flag	Coverage Δ
unittests	85.29% <ø> (+0.17%)	⬆️

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