enhancement: add format property to TOML questions

[BoyeGuillaume]

I don't believe that the formatting of the answer as LaTeX or Default should be decide on whether or not the question possesses a given tag ! We could either add a new properties in the TOML or detect certain characteristic in the text (such as "\text",```java ). We could also add a keyword in the answer that decide the type of formatting (such as if answer starts with "LaTeX" format as LaTeX) or even better parse only certain area as Latex.

Originally posted by @mredstone6 in #62 (comment)