potential solution to broken links in the docs

[shimwell]

From time to time URL links in the docs result in 404 not found errors. This happens when URLs are moved.

sphinx-build offers a linkcheck function that runs though the docs checking for broken links (both internal and external) which we can run with either of the following commands in the docs folder

sphinx-build -M linkcheck . _build

or

make linkcheck

Currently the report shows a few broken links which we can then manually fix.

We could run this check periodically or in the CI