Hook up layer tree structure with frontend (#372)

* Hook up layer tree structure with frontend (decoding and Vue are WIP)

* Fix off by one error

* Avoid leaking memory

* Parse layer structure into list of layers

* Fix thumbnail updates

* Correctly popagate deletions

* Fix selection state in layer tree

* Respect expansion during root serialization

* Allow expanding of subfolders

* Fix arrow direction

Co-authored-by: Dennis Kobert <dennis@kobert.dev>

frontend/wasm/src/api.rs

@@ -20,6 +20,11 @@ pub fn intentional_panic() {
 	panic!();
 }
 
+#[wasm_bindgen]
+pub fn wasm_memory() -> JsValue {
+	wasm_bindgen::memory()
+}
+
 /// Modify the currently selected tool in the document state store
 #[wasm_bindgen]
 pub fn select_tool(tool: String) -> Result<(), JsValue> {