WARNING: THIS MODULE OVERRIDES THE DEFAULT ROLL FUNCTION! BECAUSE OF THIS IT ISNT COMPATIBLE WITH ANY OTHER MODULE THAT DOES SOMETHING LIKE THIS.
Luck For Rolls is a module that allows costumization for the chance of critical rolls to happen in Foundry VTT.
The module can be found on the foundry vtt module installer
After installing the module it will just work in the background, tho a big part of the functionality is the costumization so I recomand you to chance the settings to your liking from the Settings -> Module Settings tab in Foundry.