Option to ignore elements with specific classes

[pawamoy]

Is your feature request related to a problem? Please describe.
It's possible to show mermaid diagrams using a mermaid class on divs. The issue is that the contents of the div is text and is therefore spell checked, triggering useless errors.

Describe the solution you'd like
An option to ignore specific classes, something like:

ignore_classes:
- mermaid
- nospellcheck

Describe alternatives you've considered
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Additional context
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