Automate the testing of tutorials to ensure cross-platform compatibility

[nomicode]

see mika's comments here:

crate/crate-tutorials#3

it's vital that our tutorials work. more so than the rest of our documentation, I would say -- because the tutorials are likely to be a user's first impression

we want the tutorials to work across the widest possible array of operating systems and setups

testing this manually each time is a hassle, and probably won't be done reliably. so, we should come up with a way of testing (i.e., executing) the tutorials automatically as part of the CI setup

not sure what the best approach is here. so creating this issue to collect thoughts, discussion, etc

[nomicode]

• See also https://github.com/crate/tech-writing-domain/issues/179.

[nomicode]

my initial thoughts:

• we have tests set up on crate/crate. I am not too familiar with the setup so I should take a look at that
• I would like to research plugins for sphinx that allow code blocks to be executed. I bet there are multiple ways of getting this working
• this would need a running instance of cratedb on the machine doing the testing. we should be able to set that up for travis or github actions

[nomicode]

• See also misc testing improvements #9.

[amotl]

We guess Jupyter Notebooks are still the most standardized way suitable for a share of use cases, at least when it comes to demonstrating and validating Python-based systems. However, it doesn't take any stance on the environment beyond the Python area, so additional infrastructure provisioning will be needed.

• https://github.com/crate/tech-writing/issues/414
• https://github.com/crate/tech-writing/issues/415
• Use Markdown or Python for writing Jupyter Notebooks cratedb-examples#135
• https://github.com/crate/devrel/issues/66