DOC: document defaults for executable config #2594
Description
Proposal
I am trying to change the frontmatter in CI depending on the jobs specifics, and would find it useful to see the defaults in the docs.
https://mystmd.org/guide/notebooks-with-markdown#execute-config
(also, it would be extremely useful if there were some easier ways to control these values (ala #2260), as what we want to ship for users can be different to what we want to do in CI and relying some sed magic to edit the tutorials is not a great workaround)
Additional notes
No response