Add multi-arch (arm64) Docker image support

[FalseFeint]

Description

The published Docker image (syllogismrxs/scrimmage:latest) is built for amd64 only. This means developers on Apple Silicon
(M1/M2/M3/M4) must run under QEMU emulation, which significantly degrades performance.

The main blocker appears to be the JSBSim dependency, which is pre-built for amd64 in the current image. JSBSim itself
supports arm64 compilation, so it should be feasible to produce a native arm64 build.

Request

Publish a multi-arch Docker manifest (linux/amd64 + linux/arm64) so that docker pull automatically selects the native
image for the host platform. This would involve:

1. Cross-compiling or natively building JSBSim for arm64
2. Building SCRIMMAGE and its dependencies for arm64
3. Using docker buildx (or similar) to produce and push a multi-arch manifest

Workaround

Running the amd64 image on arm64 via Rosetta/QEMU works but is noticeably slower, especially for simulation-heavy workloads.

Environment

• Docker image: syllogismrxs/scrimmage:latest
• Affected platforms: linux/arm64, macOS on Apple Silicon

[wfsyre]

We're working on a good cross platform docker image generation as we speak, but in the meantime you can build your own using the ci/ubuntu dockerfile in the Ubuntu-24.04 branch with the following command
docker build -f ci/dockerfiles/ubuntu --platform linux/arm64 -t scrimmage-arm64:24.04 .