Net.preload_package

```lua
Net.preload_package(area_id, asset_path)
Net.preload_package_for_player(player_id, asset_path)
```

These would act similarly to `Net.provide_asset*`, but additionally would send a packet to load the package and dependencies like `Net.initiate_encounter`.

It may make more sense to start with a copy of `Net.initiate_encounter` and remove the packet that starts the battle.