Update PDFgui user guide #167
Description
PDFgui user guide has not been updated since 2.0 release (May 2023). We might want this to be deployed along with the api document. There are also contents that need to be updated (e.g. things that related to setup.py which we replace with pyproject.toml).
The PDFgui user guide was made using texi2html 5.0 and deployed on https://www.diffpy.org/doc/pdfgui/index.html. This is also not aligned with the new deploy namespace (which it should be something like https://www.diffpy.org/pdfgui/...). Maybe we should change this and delete the older resource. Also remember to update all the links in the user guide.
@sbillinge I also found out that the new vs. old document namespace is happening in other packages too. For example we deployed the new diffpy.structure api on https://www.diffpy.org/diffpy.structure/, but using similar pattern from the above old pdfgui link I found the older api documents on https://www.diffpy.org/doc/structure/, which is showing 3.1.0 as the latest version (which should be 3.2.0 now). This might not be an issue if users follow readme, but it might be problematic in general because I see both when searching 'diffpy.structure api' on google.