feat(notifications_app): Display rich notifications

[provokateurin]

Closes #212

[codecov]

Codecov Report

Attention: Patch coverage is 97.70115% with 2 lines in your changes missing coverage. Please review.

Project coverage is 28.38%. Comparing base (c999f28) to head (b288377).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...otifications_app/lib/src/widgets/notification.dart	90.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2456      +/-   ##
==========================================
+ Coverage   28.37%   28.38%   +0.01%     
==========================================
  Files         352      353       +1     
  Lines      135903   135922      +19     
==========================================
+ Hits        38559    38585      +26     
+ Misses      97344    97337       -7     

Flag	Coverage Δ		*Carryforward flag
account_repository	98.76% <ø> (ø)
cookie_store	99.48% <ø> (ø)		Carriedforward from c999f28
dashboard_app	96.05% <ø> (ø)
dynamite	31.08% <ø> (ø)		Carriedforward from c999f28
dynamite_end_to_end_test	61.69% <ø> (ø)		Carriedforward from c999f28
dynamite_runtime	85.40% <ø> (ø)		Carriedforward from c999f28
neon_dashboard	96.05% <ø> (ø)		Carriedforward from c999f28
neon_framework	59.27% <100.00%> (+2.19%)	⬆️
neon_http_client	96.69% <ø> (ø)		Carriedforward from c999f28
neon_notifications	100.00% <ø> (ø)		Carriedforward from c999f28
neon_talk	99.45% <ø> (ø)		Carriedforward from c999f28
nextcloud	24.14% <ø> (ø)		Carriedforward from c999f28
notifications_app	97.40% <90.00%> (-2.60%)	⬇️
sort_box	90.90% <ø> (ø)		Carriedforward from c999f28
talk_app	98.94% <100.00%> (-0.15%)	⬇️

*This pull request uses carry forward flags. Click here to find out more.

Files with missing lines	Coverage Δ
...framework/lib/src/widgets/rich_text/deck_card.dart	100.00% <100.00%> (ø)
..._framework/lib/src/widgets/rich_text/fallback.dart	100.00% <100.00%> (ø)
...neon_framework/lib/src/widgets/rich_text/file.dart	100.00% <100.00%> (ø)
...n_framework/lib/src/widgets/rich_text/mention.dart	100.00% <100.00%> (ø)
...framework/lib/src/widgets/rich_text/rich_text.dart	100.00% <100.00%> (ø)
...ork/packages/talk_app/lib/src/widgets/message.dart	98.80% <100.00%> (-0.21%)	⬇️
...otifications_app/lib/src/widgets/notification.dart	95.65% <90.00%> (-4.35%)	⬇️

... and 3 files with indirect coverage changes