Use starter project to set up players joining

[AngelOnFira]

The example Godot Ball (https://app.graphite.dev/github/pr/rivet-gg/examples/17/Add-godot-ball-example) can be used as a starting place. The example includes basic code to create a scene for each player, and automatically connect to a server. For the Agario clone, we should probably leave it at auto-joining a server so that lobbies aren't the focus of too much.

[linear[bot]]

GDT-110 Use starter project to set up players joining