feat: implement save all

src/states/konvaStage.svelte.ts

@@ -0,0 +1,16 @@
+import type { Stage } from "svelte-konva";
+
+function createState() {
+  let stage: Stage | undefined = $state(undefined);
+
+  return {
+    get stage(): Stage | undefined {
+      return stage;
+    },
+    set stage(newStage: Stage) {
+      stage = newStage;
+    },
+  };
+}
+
+export const konvaStageState = createState();