add DAT links for the various MAME cores

[markwkidd]

This follows on the useful addition of the FinalBurn DAT link added in this PR https://github.com/libretro/docs/pull/384

At the moment there should now be DAT files for each of the MAME cores included in their respective repositories that can also be linked here. I'm taking time away from this project and many others for health reasons at the moment but I hate to lose track of a todo that is right in my wheelhouse.