fix: use text state

src/states/theme.svelte.ts

@@ -0,0 +1,16 @@
+export type Theme = "dark" | "light";
+
+function createThemeState() {
+  let current: Theme = $state("dark");
+
+  return {
+    get theme() {
+      return current;
+    },
+    toggle() {
+      current = current === "dark" ? "light" : "dark";
+    },
+  };
+}
+
+export const themeState = createThemeState();