Add Vitest tests for the languages, router, footer and pages, and a lint:check script

package.json

@@ -8,6 +8,9 @@
     "build": "vite build",
     "preview": "vite preview",
     "lint": "eslint . --fix",
+    "lint:check": "eslint .",
+    "test": "vitest run",
+    "test:watch": "vitest",
     "format": "prettier --write \"src/**/*.{js,vue,css,json}\""
   },
   "dependencies": {
@@ -29,12 +32,15 @@
   "devDependencies": {
     "@vitejs/plugin-vue": "^6.0.2",
     "@vue/eslint-config-prettier": "^10.2.0",
+    "@vue/test-utils": "^2.5.1",
     "eslint": "^9.39.1",
     "eslint-config-prettier": "^10.1.8",
     "eslint-plugin-prettier": "^5.5.4",
     "eslint-plugin-vue": "^10.6.2",
+    "jsdom": "^29.1.1",
     "prettier": "^3.7.3",
     "tw-animate-css": "^1.4.0",
-    "vite": "^8.0.16"
+    "vite": "^8.0.16",
+    "vitest": "^4.1.11"
   }
 }