Jupyter app integration tests

[jayqi]

Adds integration tests to check that installing post-save hook works with various Jupyter apps.

Additional minor changes:

• Adds Python 3.11 to test matrix
• Changes conda channel to conda-forge. This had been previously in #85 due to Python 3.6 issues, but those are no longer relevant.
• Bumps the Python version in non-matrix test steps to 3.9

[codecov-commenter]

Codecov Report

Merging #108 (b3bf80b) into master (977b595) will not change coverage. The diff coverage is n/a.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #108 +/- ## ====================================== Coverage 98.5% 98.5% ====================================== Files 8 8 Lines 425 425 ====================================== Hits 419 419 Misses 6 6 ```

[github-actions[bot]]

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