Uxr SeeThrough For Pico

Its a basic attempt to apply Ultimate XR framwork on Pico with See-through feature. Known issues: - Unsatisfying lighting quality because of the heaviness of the demo scene. - Bugs with controller buttons after a pause, like pressing home button and resume the app. More about Ultimate XR: https://www.ultimatexr.io/ 这是Ultimate XR在Pico上的尝试应用，具有 See-through 功能 已知问题： - 因为场景过大引起的光照效果不佳； - 应用暂停后引起的控制器按钮Bug, 比如按下Home键暂停然后继续应用后； 了解更多关于 Ultimate XR:https://www.ultimatexr.io/