Enable Spell check in megalinter

[BryanQuigley]

No description provided.

[adamdmharvey]

Happy to grab this one. One of the challenges is all of the city names, maintainer names, etc, so the resulting custom dictionary file for CSpell gets quite large. It'll self generate a dictionary, but future additions of new datasets may have some additional friction as valid terms in the YAML front matter metadata will need to be potentially added.

Perhaps step one as adding it but not linting the datasets/ dir, and then a second round to tackle that?

[BryanQuigley]

Starting small makes sense to me. My better lint script just has it check the changes done and not everything - will try to dig that up.

This might also be something that we should push to upstream