automatically calculate base combat values

src/module/migrations/0-1-0.ts

@@ -0,0 +1,28 @@
+export async function migrate(): Promise<void> {
+    for (const a of game.actors.entities) {
+        const updateData = getActorUpdateData();
+        console.log(`Migrating actor ${a.name}`);
+        await a.update(updateData, { enforceTypes: false });
+    }
+}
+
+function getActorUpdateData(): Record<string, unknown> {
+    const updateData = {
+        data: {
+            combatValues: [
+                "hitPoints",
+                "defense",
+                "initiative",
+                "movement",
+                "meleeAttack",
+                "rangedAttack",
+                "spellcasting",
+                "targetedSpellcasting",
+            ].reduce((acc, curr) => {
+                acc[curr] = { "-=base": null };
+                return acc;
+            }, {}),
+        },
+    };
+    return updateData;
+}