Proper caching for loaded WI

- Implement StructurecCloneMap, which is a map that provides structured clones on both get and set
- Don't delete WI cache on save, but update the cache
- Ensure that cache is updated immediately, so any future get will load the new saved data already
- Still be consistent with clones, so requested cache data that wasn't saved isn't taken into account

public/scripts/util/StructuredCloneMap.js

@@ -0,0 +1,36 @@
+/**
+ * A specialized Map class that provides consistent data storage by performing deep cloning of values.
+ *
+ * @template K, V
+ * @extends Map<K, V>
+ */
+export class StructuredCloneMap extends Map {
+    /**
+     * Adds a new element with a specified key and value to the Map. If an element with the same key already exists, the element will be updated.
+     *
+     * The set value will always be a deep clone of the provided value to provide consistent data storage.
+     *
+     * @param {K} key - The key to set
+     * @param {V} value - The value to set
+     * @returns {this} The updated map
+     */
+    set(key, value) {
+        const clonedValue = structuredClone(value);
+        super.set(key, clonedValue);
+        return this;
+    }
+
+    /**
+     * Returns a specified element from the Map object.
+     * If the value that is associated to the provided key is an object, then you will get a reference to that object and any change made to that object will effectively modify it inside the Map.
+     *
+     * The returned value will always be a deep clone of the cached value.
+     *
+     * @param {K} key - The key to get the value for
+     * @returns {V | undefined} Returns the element associated with the specified key. If no element is associated with the specified key, undefined is returned.
+     */
+    get(key) {
+        const value = super.get(key);
+        return structuredClone(value);
+    }
+}