Sanitizing special chars in markdown file paths

[Mzack9999]

Proposed changes

This PR replaces ? with _ in markdown filename export

Checklist

• Pull request is created against the dev branch
• All checks passed (lint, unit/integration/regression tests etc.) with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[sullo]

Having a further thought, I'd recommend we replace the following as they can be problematic on both Win/*nix:
/ > | : ; * > " '

I think this will cover any characters in a file name which could be problematic for a shell to manipulate them without adding quotes.

Also, :space: can be considered as well since it's annoying :)

Windows has more restrictions, but I don't think we need to account for every possible thing (e.g., "CON").