Add v12 support

modules/heritiers-main.js

@@ -46,10 +46,8 @@ Hooks.once("init", async function () {
   CONFIG.Combat.documentClass = HeritiersCombat
   CONFIG.Actor.documentClass = HeritiersActor
   CONFIG.Item.documentClass = HeritiersItem
-  // Create an array of values from 0 to 10 
-  HERITIERS_CONFIG.listNiveau = Array.from({ length: 11 }, (v, k) => k)
   // Create an object of bonus/malus from -6 to +6 signed
-  HERITIERS_CONFIG.bonusMalus = Array.from({ length: 7 }, (v, k) => k - 6)
+  HERITIERS_CONFIG.bonusMalus = Array.from({ length: 7 }, (v, k) => toString(k - 6))
   game.system.lesheritiers = {
     HeritiersUtility,
     config: HERITIERS_CONFIG