Updated docs not published

[nkeim]

It looks like the GitHub action to build the docs is successfully building the HTML docs, but then failing on the "Publish" step (which I believe would push the docs to the gh-pages branch of the repository). In the log, it appears that the "Publish" step produces no output, presumably because of the conditional

if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}

AFAICT both conditions are being satisfied when we merge something into the main branch.

Meanwhile, it looks like the gh-pages branch is getting overwritten anyway with only an empty .nojekyll file.

The configuration options for this action look reasonable as per the documentation.

Once this is working, we can solve the problem of whether to host releases' documentation in the pims gh-pages branch, or at the current location linked to in the README.