test: appendHtml utility

[fbasso]

This utility is designed to help writing unit test with vitest, by providing html string to create node element and append them to a container in one line.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.61%. Comparing base (72b6ebc) to head (cf312ee).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1258      +/-   ##
==========================================
+ Coverage   90.59%   90.61%   +0.01%     
==========================================
  Files         117      117              
  Lines        3393     3399       +6     
  Branches      550      551       +1     
==========================================
+ Hits         3074     3080       +6     
  Misses        202      202              
  Partials      117      117              

Flag	Coverage Δ
e2e	81.76% <16.66%> (-0.12%)	⬇️
unit	84.74% <100.00%> (+0.03%)	⬆️

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