Documentation build workflow

[krzywon]

The sasmodels docs are curently only built via the sasview workflows. This means any changes to documentation done in this repo remain untested until the changes are in the master branch and a workflow is triggered in sasview.

I suggest we add a separate job to the current workflow file that builds the documentation on push and PR to ensure the documentation builds successfully.

[krzywon]

Disregard my original post - the docs are already built for linux. Should we enable the builds for other platforms as well?

Storing the as-built documentation for review would be a helpful addition.

[llimeht]

I don't think there's any need to build the docs on other platforms - the docs shouldn't be platform specific and so the fastest architecture is a reasonable pick.

The docs do exercise the code somewhat... but if that's needed for testing purposes, then that's a sign for more tests :)

Publishing the documentation somewhere like readthedocs would certainly be an excellent idea.