AV2 decoder 1

The AV2 decoder of Immuch360 Desktop (experimental): immuch360-av2, our program on the library of dav2d by VideoLAN (BSD-2-Clause), for Windows x64, Linux x64 and macOS (Apple silicon and Intel), built and checked by our CI from pinned sources; the Windows program is signed by APROGSYS. It decodes AV2 videos with the processor and serves the pictures to the video player of the app on this computer only. This is not a release of the app: the app downloads the archive of its computer when an AV2 video plays without it, checks it by its SHA-256, and works offline afterwards. Licences, files and sources: AV2-DECODER-LICENSES.md. Sums: SHA256SUMS.