feat(neon_talk): Display icon next to deleted messages

[provokateurin]

Makes it a lot clearer that it is not a normal chat message.

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 44.63%. Comparing base (d49045a) to head (955e6eb).
Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1826      +/-   ##
==========================================
+ Coverage   44.55%   44.63%   +0.07%     
==========================================
  Files         114      114              
  Lines        3795     3802       +7     
==========================================
+ Hits         1691     1697       +6     
- Misses       2104     2105       +1     

Files	Coverage Δ
...ckages/neon/neon_talk/lib/src/widgets/message.dart	100.00% <100.00%> (ø)
packages/neon_framework/lib/src/theme/icons.dart	16.21% <0.00%> (-0.46%)	⬇️

[Leptopoda]

I'm not 100% convinced by the design:

1. the icon is bigger than the text
2. there should be a space between the icon and the icon and the text for better readability