Add keep-validation to latex and typst for accessibility validation

[hcc-donder]

Description

There are already options for keep-tex and keep-md. There should also be an option for keeping the validation run output (keep-validation). This could be a string option of "raw", "xml", "text", "html", or "json" (these are the format options for verapdf). Or it could be T/F like the other keep- flags with an additional keep-validation-format for specifying the output format.

This would allow me to keep proof in the same output folder as my PDF, indicating that the PDF has already been validated and passes validation.