add eslint and prettier

backend/eslint.config.js

@@ -0,0 +1,24 @@
+import js from "@eslint/js";
+import globals from "globals";
+import { defineConfig } from "eslint/config";
+
+export default defineConfig([
+  {
+    files: ["**/*.{js,mjs,cjs}"],
+    plugins: { js },
+    extends: ["js/recommended"],
+    languageOptions: {
+      globals: globals.node
+    },
+    rules: {
+      "no-unused-vars": [
+        "error",
+        {
+          argsIgnorePattern: "^_",
+          varsIgnorePattern: "^_",
+          caughtErrorsIgnorePattern: "^_",
+        },
+      ]
+    }
+  },
+]);