deprecate mod_data #239
Description
in #218, mod_data was moved from ModLoader to ModLoaderStore
in #233, we found out a way to deprecate variables. the same method should be applied here
Additionally, we should provide a proper way to get information about wether a mod is installed and active or disabled.
something along the lines of is_mod_installed / is_mod_active in either ModLoaderMod or ModLoader itself
removed in favour of #219