use relative path in navigation.json

en_us/navigation.json

@@ -37,7 +37,7 @@
             [
                 {
                     "text": "中文 Chinese",
-                    "target": "https://tamlok.github.io/vnote/zh_cn/"
+                    "target": "../zh_cn/"
                 }
             ]
         }

zh_cn/navigation.json

@@ -37,7 +37,7 @@
             [
                 {
                     "text": "English",
-                    "target": "https://tamlok.github.io/vnote/en_us/"
+                    "target": "../en_us/"
                 }
             ]
         }