Need user documentation and guides

[newville]

As from the QD webinar today, this module really needs a user guide for describing setup of the IOC and usage, including the various triggering and collection modes.

It would be interesting to know whether using the Github Wiki or writing static Sphinx documentation was preferred.

[newville]

@TomQD-94 I started docs using Github gh-pages with Sphinx, with source in documentation/source and initial results at
https://epics-modules.github.io/xspress3/

[TomQD-94]

@newville Great thanks, I will start putting the information I have into these pages