Netplay not synced when using start function
I was initializing my game inside the `start` callback, but this lead to a memory access error when trying to use netplay, or if I defined empty arrays at declaration like `let players: Player[] = [];` then the game would render but with entities missing on the client player's side. The host would see all the entities as well as inputs from the client player, but the client's game was broken.
I fixed it by moving initialization out of `start` and doing it at top level.
Is `start` just not supported yet for netplay?
This is a very cool feature, by the way! I love how simple you're trying to make it.

Here's my game for reference: https://github.com/1j01/polywogg
If you check out [bcbf7aaa43](https://github.com/1j01/polywogg/tree/bcbf7aaa434d55a407131ebe954bd0797118753b) (before [this workaround commit](https://github.com/1j01/polywogg/commit/3fa8889fa3aaf238b3fb6bc3700f5ce4f0ef9b39)) you can see this issue.