Improve documentation-related CI jobs
This MR:
- Improves the documentation -related CI jobs by moving the doctest and linkcheck into a separate job.
- In the past, broken links ended up letting the whole pipeline fail, which is a bit … drastic. While a failing documentation build should really fail, a broken link is outside of our control, so it's okay to have
allow_failure: true.
- In the past, broken links ended up letting the whole pipeline fail, which is a bit … drastic. While a failing documentation build should really fail, a broken link is outside of our control, so it's okay to have
- Reduces number of nodes and edges in Opinionet documentation plot; this should speed up docs generation via CI (addressing part of #368).