Add Storage Collection docs

docs/manual/15 Storage Collections.md

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+# Storage Collections
+DATEX allows the usage of native Set and Map objects. Those types are stored in RAM and may impact performance when it's data is getting to large.
+For this reason DATEX provides special storage collections that allow the handling of massive amounts of data more efficiently.
+
+The API is similar to the native JavaScript collections with the major difference that their instance methods are asynchronous.
+To get the size of the collection it is recommended to use the asynchronous `getSize` method.
+
+> [!NOTE]
+> The storage collections are not stored persistently by default. To store persistent data refer to [Eternal Pointers](./05%20Eternal%20Pointers.md).
+
+## StorageSet
+```ts
+import "datex-core-legacy/types/storage-set.ts";
+const mySet = new StorageSet<number>();
+await mySet.add(123); // Add 123 to the StorageSet
+
+for await (const entry of mySet) { // Iterate over values
+    console.log(entry);
+}
+
+await mySet.getSize(); // Returns the size of the StorageSet (1)
+await mySet.clear(); // Clear StorageSet
+```
+
+## StorageMap
+```ts
+import "datex-core-legacy/types/storage-map.ts";
+const myMap = new StorageMap<string, number>();
+await myMap.set("myKey", 123); // Add key 'myKey' with value 123 to the StorageMap
+
+for await (const [key, value] of myMap) { // Iterate over entries
+    console.log(key, value);
+}
+
+await mySet.getSize(); // Returns the size of the StorageMap (1)
+await myMap.clear(); // Clear StorageMap
+```