U2024.01.02-0622: Automatic merge of T1.5.1-794-g4cad06780 and 14 pull requests

- Pull request #570 at 3539862b4: Experimental glTF 2.0 support with PBR lighting
- Pull request #839 at d00beb983: First phase of https://blueprints.launchpad.net/or/+spec/additional-cruise-control-parameters
- Pull request #876 at f92de7665: docs: add source for documents previously on website to source Documentation folder
- Pull request #882 at a055bca64: Blueprint/train car operations UI window
- Pull request #885 at 8f9433364: feat: Add notifications to Menu
- Pull request #886 at 6c0785b6c: Scene viewer extension to TrackViewer
- Pull request #892 at 1f5ba4c81: Signal Function OPP_SIG_ID_TRAINPATH
- Pull request #896 at 5866028cf: First implementation of https://blueprints.launchpad.net/or/+spec/specific-sounds-for-ai-trains
- Pull request #897 at 0a9d93913: feat: Improved system information collection
- Pull request #899 at 8be310d54: Duplex steam engines - Booster Engine addition
- Pull request #903 at 7353625d9: Downloading route content (Github, zip)
- Pull request #906 at 58506605e: Bug fix for https://bugs.launchpad.net/or/+bug/2047299 Crash loading a 3Dcab-only loco
- Pull request #907 at 9b0b04faf: Bug fix for https://bugs.launchpad.net/or/+bug/2047300 Dynamic tracks disappear after long tunnel
- Pull request #908 at 4b4afe311: feat: supports switching adhesion precisions