fix: prevent hiding floating date separator in message lists

[MartinCupela]

🎯 Goal

Based on Jurgen's review changed the behavior of floating separator which now will be displayed always at the top and just change the value to the date corresponding to the section above the viewport for which the inlined date separator is not yet visible.

🎨 UI Changes

ejhO.webm

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.25%. Comparing base (5f9ee0d) to head (081b8d0).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3119      +/-   ##
==========================================
- Coverage   82.25%   82.25%   -0.01%     
==========================================
  Files         418      418              
  Lines       12096    12086      -10     
  Branches     3891     3886       -5     
==========================================
- Hits         9950     9941       -9     
+ Misses       2146     2145       -1     

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[github-actions]

Size Change: -93 B (-0.02%)

Total Size: 620 kB

📦 View Changed

Filename	Size	Change
dist/cjs/index.js	238 kB	-41 B (-0.02%)
dist/es/index.mjs	236 kB	-52 B (-0.02%)

ℹ️ View Unchanged

Filename	Size
dist/cjs/audioProcessing.js	1.32 kB
dist/cjs/emojis.js	3.01 kB
dist/cjs/mp3-encoder.js	1.27 kB
dist/cjs/WithAudioPlayback.js	44.4 kB
dist/css/emoji-picker.css	188 B
dist/css/emoji-replacement.css	456 B
dist/css/index.css	46.3 kB
dist/es/audioProcessing.mjs	1.31 kB
dist/es/emojis.mjs	2.52 kB
dist/es/mp3-encoder.mjs	756 B
dist/es/WithAudioPlayback.mjs	44.2 kB

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