Save references to asyncio tasks

[TheTechromancer]

Fixes potential bug described here:

https://textual.textualize.io/blog/2023/02/11/the-heisenbug-lurking-in-your-async-code/

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 93%. Comparing base (6e9eef5) to head (28d91ea).
Report is 3 commits behind head on dev.

Files with missing lines	Patch %	Lines
bbot/cli.py	0%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##             dev   #2125   +/-   ##
=====================================
+ Coverage     93%     93%   +1%     
=====================================
  Files        372     372           
  Lines      28787   28787           
=====================================
+ Hits       26581   26582    +1     
+ Misses      2206    2205    -1     

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