feature(chat): add the ability to ping a matrix room

[gounux]

Basically the title.

Several tests run to get the following on matrix / element :

🥵

[codecov-commenter]

Codecov Report

❌ Patch coverage is 38.88889% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.73%. Comparing base (4ba212e) to head (5ed7636).

Files with missing lines	Patch %	Lines
gischat/dispatchers.py	22.22%	7 Missing ⚠️
gischat/app.py	0.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #105      +/-   ##
==========================================
- Coverage   80.75%   79.73%   -1.03%     
==========================================
  Files           6        6              
  Lines         582      597      +15     
  Branches       45       46       +1     
==========================================
+ Hits          470      476       +6     
- Misses        100      108       +8     
- Partials       12       13       +1     

Flag	Coverage Δ
unittests	79.73% <38.88%> (-1.03%)	⬇️

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