re-enable spellcheck, or at least have a linter

I think it'd be great to remove typos in the docs. For this, we introduced the action (which is manually disabled at the moment).

We can

- make the action more useful by whitelisting more chemistry vocabs to the whitelist
- ask contributors to run a linter/install some spellchecking extension

Start by locating the manually disabled spellcheck action and reviewing how its whitelist is configured. Decide whether to make the action useful with additional chemistry vocabulary or document a contributor linter/spellchecking workflow; done means the chosen approach is available for contributors and catches documentation typos.

Written by the indexing model from the issue text.