Clean up echo kernel handling and update readme

[blink1073]

No description provided.

[codecov]

Codecov Report

Base: 94.70% // Head: 94.79% // Increases project coverage by +0.09% 🎉

Coverage data is based on head (6be77eb) compared to base (e833bf8).
Patch coverage: 94.73% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #22      +/-   ##
==========================================
+ Coverage   94.70%   94.79%   +0.09%     
==========================================
  Files          10       10              
  Lines         453      461       +8     
==========================================
+ Hits          429      437       +8     
  Misses         24       24              

Impacted Files	Coverage Δ
pytest_jupyter/jupyter_server.py	92.93% <83.33%> (+0.07%)	⬆️
pytest_jupyter/jupyter_client.py	92.98% <100.00%> (+0.12%)	⬆️
tests/test_jupyter_client.py	100.00% <100.00%> (ø)
tests/test_jupyter_server.py	100.00% <100.00%> (ø)

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