Add Jupyter-black to `check/format`

[vtomole]

Description of the issue
Some indentation in our Jupyter notebooks are inconsistent (See #3729). Adding jupyter-black to our CI will catch this issue early.

[vtomole]

@paniash I've just assigned it to you. Thanks!

[paniash]

@vtomole Thanks! I'm fairly new to the concept of unit tests and would be glad if you could provide me some pointers.

Looking at the test code, I get the idea of running jupyter-black on the .ipynb files but the repo doesn't seem (or atleast I didn't find any) to have any instructions on running it from the commandline. Just using black and a wrapper around it to form a jupyter extension. Could you help me with this?

[vtomole]

@vtomole It seems like you can't run it from the command-line. We might want black-nb instead. Please confirm that it does what we want.

[anonymousr007]

Hi @vtomole, This issue is still open means check/nbformat already in the codebase, Can you elaborate little bit more ?

[vtomole]

Please look at #4020 (review) for context.