Add ipynb outputs and data, pcmt, workflows

[Tieqiong]

@sbillinge please check, thanks!

ipynb:
- Add examples outputs.
- Add examples data files into ./examples/data, update paths accordingly.
- Copy cpd-1a.prn from iucr, add attributions in header and skip header accordingly during read file.
pcmt:
- Remove nbstripout.
- Remove codespell check for ipynb, use nbqa supported codespell instead.

Add attributes to iucr file in README.rst.
Revert powderpattern.py plot functions, add #noqa for now.
Correct authors.
Try trigger workflows without .github on main.

closes #54

[vincefn]

Note that the notebooks need to be stored pre-rendered, because when relying on ipympl, I don't think the rendering can be done in a non-interactive environment.

[sbillinge]

Ths LGTM. I am not sure how to do the pre-rendering that @vincefn mentions, but @Tieqiong please could you try and take care of that and I can merge this.