add reference labels

[oliver-sanders]

Add a couple of labels so we can reference these sections from other places.

Requirements check-list

• I have read CONTRIBUTING.md and added my name as a Code Contributor.

[oliver-sanders]

Test failures are unrelated. Fixed on #682

They are the result of spellchecking running over the API docs and complaining about variable names like kwargs and cfg.

As we expand our API docs, spellchecking is going to be increasingly difficult to manage.

[wxtim]

Test failures are unrelated. Fixed on #682

They are the result of spellchecking running over the API docs and complaining about variable names like kwargs and cfg.

As we expand our API docs, spellchecking is going to be increasingly difficult to manage.

Yes. Sadly.

Although I think that it's worth considering whether non dictionary words are reasonable in code: I think that (at least in this project) we recognise ctx, cfg and kwargs such that it's reasonable to use them. But if spellchecker starts catching us using weird/obscure terms/contractions then we should probably consider whether those are OK.

[oliver-sanders]

Although I think that it's worth considering whether non dictionary words are reasonable in code

Yes they are!