Added error message box when SteamVR OpenXR could not be found — Vermillion - VR Painting Steam update #80111

Some users don't have the correct OpenXR configuration for SteamVR, which leads to Vermillion not launching into VR or causing graphical glitches. To keep this from happening, the default Steam version of Vermillion will now no longer launch if SteamVR OpenXR was not detected. You will instead be directed to the support page with instructions, and a button to join the Discord for support if required.