Mention code highlighting in Markdown and ChatFeed

[ahuang11]

I'm not sure if admonitions can be used in Reference notebooks?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.91%. Comparing base (864a514) to head (6e5a9fc).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6519   +/-   ##
=======================================
  Coverage   82.91%   82.91%           
=======================================
  Files         313      313           
  Lines       45902    45902           
=======================================
+ Hits        38060    38061    +1     
+ Misses       7842     7841    -1     

Flag	Coverage Δ
ui-tests	40.09% <ø> (-0.01%)	⬇️
unitexamples-tests	71.13% <ø> (+<0.01%)	⬆️

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[philippjfr]

Yes, let's use them, but let's go for the ::: syntax to make it clear that this is special syntax.

[ahuang11]

Is :::{note} what you meant? Or is there :::{admonition}

[philippjfr]

Let's go with :::{note}

[ahuang11]

Okay, I think it's ready then.