[fix] DataStorage: create data/dict to prevent Android crash

```
08-12 14:32:17.325  9188  9216 E luajit-launcher: Failed to run script: frontend/util.lua:291: cannot open /storage/emulated/0/koreader/data/dict: No such file or directory
08-12 14:32:17.333  9188  9216 V threaded_app: android_app_destroy!
```

datastorage.lua

@@ -35,7 +35,7 @@ end
 
 local function initDataDir()
     local sub_data_dirs = {
-        "cache", "clipboard", "data", "history",
+        "cache", "clipboard", "data", "data/dict", "history",
         "ota", "screenshots", "settings",
     }
     for _, dir in ipairs(sub_data_dirs) do