Do we need to embed metadata in the markdown prose sections?

[rprimet]

For instance, to add directives for catdev such as exemptions from linting (like noqa in flake), or to indicate how to process images when they have been manually converted to latex formulas etc.

If so, how? Should we use code fences with a specific identifier (e.g. ```catdev)?

[denismerigoux]

Issue related to CatalaLang/catala#392. I don't have any strong opinions on this. @AltGr ?