Add make tutorial to docs CI workflow

[eb8680]

Motivated by off-target Sphinx build errors in #3006. Can't remember if there was a reason we weren't doing this, feel free to close if there was one...

[eb8680]

Not sure what's going on, but the tutorial HTML build is taking forever on the GitHub CI machines. I might have to move this to a separate stage to avoid a big increase in CI turnaround time.

[fritzo]

taking forever

that's probably the reason we didn't add this to ci

[eb8680]

Still, even on my slow personal laptop make tutorial runs in seconds with no cached builds - there's no way GitHub should be taking 25+ minutes.

[eb8680]

@fritzo can you take a look at this again? I was helping someone today with issues building the example HTML and this seemed like it would be a useful check to rule out bugs in the tutorials as a cause of build issues versus incorrect versions of Sphinx and related dependencies.

Not sure what's going on, but the tutorial HTML build is taking forever on the GitHub CI machines

This seems to be resolved by not using multiple Sphinx workers (i.e. removing the -j 8 argument from the Sphinx build).