Update login description

Author: kitloong

src/locales/en/lang.json

@@ -10,7 +10,7 @@
     "forgot_password": "Forgot password?",
     "signup": {
       "title": "Sign up",
-      "description": "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod\ntempor incididunt ut labore et dolore magna aliqua."
+      "description": "This is a demo page for https://github.com/kitloong/nextjs-dashboard. Click \"Login\" to view the full dashboard preview."
     },
     "message": {
       "auth_failed": "Invalid username or password"

src/locales/ja/lang.json

@@ -10,7 +10,7 @@
     "forgot_password": "パスワードを忘れましたか？",
     "signup": {
       "title": "サインアップ",
-      "description": "いろはにほへとちりぬるをわかよたれそつねならむ\nうゐのおくやまけふこえてあさきゆめみしゑひもせす"
+      "description": "これは https://github.com/kitloong/nextjs-dashboard のデモページです。「ログイン」をクリックすると、ダッシュボードの全体プレビューを表示できます。"
     },
     "message": {
       "auth_failed": "認証に失敗しました"

src/locales/zh/lang.json

@@ -10,7 +10,7 @@
     "forgot_password": "忘记密码?",
     "signup": {
       "title": "注册",
-      "description": "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod\ntempor incididunt ut labore et dolore magna aliqua."
+      "description": "这是 https://github.com/kitloong/nextjs-dashboard 的演示页面。点击“登录”即可查看完整的仪表板预览。"
     },
     "message": {
       "auth_failed": "用户名或密码无效"