Add Telegram HTML formatting support

[timkpaine]

No description provided.

[github-actions]

Test Results

1 470 tests  +11   1 446 ✅ +11   25s ⏱️ -6s
    1 suites ± 0      24 💤 ± 0 
    1 files   ± 0       0 ❌ ± 0 

Results for commit c16cc31. ± Comparison against base commit 321891d.

[codecov]

Codecov Report

❌ Patch coverage is 77.77778% with 60 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.24%. Comparing base (321891d) to head (c16cc31).

Files with missing lines	Patch %	Lines
chatom/format/telegram.py	74.44%	18 Missing and 5 partials ⚠️
chatom/format/text.py	36.36%	12 Missing and 9 partials ⚠️
chatom/discord/backend.py	40.00%	7 Missing and 5 partials ⚠️
chatom/format/attachment.py	33.33%	1 Missing and 1 partial ⚠️
chatom/telegram/backend.py	83.33%	0 Missing and 1 partial ⚠️
chatom/telegram/message.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #85      +/-   ##
==========================================
+ Coverage   77.19%   77.24%   +0.04%     
==========================================
  Files         127      130       +3     
  Lines       20555    20802     +247     
  Branches     1700     1744      +44     
==========================================
+ Hits        15867    16068     +201     
- Misses       4342     4361      +19     
- Partials      346      373      +27     

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