Support converting Jupyter Notebooks

[EwoutH]

It would be amazing if flynt would also be able to replace the old string formats in Jupyter Notebooks (.ipynb files)!

[ikamensh]

Hi, I agree that would be a desirable feature. But the effort to implement it might also be high; will update the issue once I have progress or at least a plan for it.

[janosh]

Might be worth taking a look at nbqa. They've adopted a lot of other tools to notebooks.