add cache.

src/oj/composables/code.ts

@@ -1,6 +1,8 @@
+import { STORAGE_KEY } from "~/utils/constants"
+import storage from "~/utils/storage"
 import { Code } from "~/utils/types"
 
 export const code = reactive<Code>({
   value: "",
-  language: "C",
+  language: storage.get(STORAGE_KEY.LANGUAGE) || "C",
 })