Visible Offhand

- Added configuration option "handheldItems", the default is "minecraft:filled_map", can be filled in a new value (id:item) to tell the Mod that the main hand holding these items will not force Offhand rendering
```
//The default content in the "visible_offhand.json" configuration file:
{
  "doubleHands": true,
  "handheldItems": [
    "minecraft:filled_map"
  ]
}

```
- Replace the "Done" button in the "Skin Customization" screen with the "Reload Profile/Done" button, and you can re-read the configuration information in the configuration file at any time during the game