#5 two small fixes and extra Oculus support

Fixed not being able to fuel booster after landing.

Limited the value range for the integrating part of the PID controller. Before it could run into a min/max float error when using extreme values for Ti and Tt.

Also added a second Windows build with Unity's Oculus plugin instead of the OpenXR plugin. Hopefully it works better with Oculus devices.

I also updated to the newest Unity version 2021.2.6f1. So there might be new bugs, which we don't know yet. Therefore I left the earlier Windows version available to download for the moment. Linux and Mac will come later as there seem to be specific problems for them.