add special creature ability as item type

src/module/common/common-data.ts

@@ -0,0 +1,15 @@
+export interface ModifiableData<T> {
+    base: T;
+    mod: T;
+    total?: T;
+}
+
+export interface ResourceData<T> extends ModifiableData<T> {
+    value: T;
+    max?: T;
+}
+
+export interface UsableResource<T> {
+    total: T;
+    used: T;
+}