https://wccftech.com/red-dead-redemption-2-script-hook/

Red Dead Redemption 2 has only been available for less than a month on PC, and the mods currently available for the game don't change things up too much. This, however, is about to change.

Alexander Blade has now released the Red Dead Redemption 2 Script Hook, a library that allows script native functions in custom .asi plugins. Alexander's Blade Grand Theft Auto V Script Hook has been used for most major mods released for the game, so we should expect the same thing happening for Red Dead Redemption 2.