Update svMultiPhysics documentation with Docker image link (simvascular/svmultiphysics)

[sujaldave]

The Docker image for the SimVascular solver has recently been renamed from:

simvascular/solver

to:

simvascular/svmultiphysics

to better reflect the underlying GitHub repository (svMultiPhysics) and avoid confusion.

The updated Docker image is available here:
https://hub.docker.com/r/simvascular/svmultiphysics

We should update the svMultiPhysics documentation on the SimVascular website to include this link and reflect the new naming convention. This will help users easily locate and use the correct Docker image.

[ktbolt]

@sujaldave The svMultiPhysics Docker container is documented in the svMultiPhysics README file, not in the SimVascular web svMultiPhysics documentation.

I think I will add a Docker section to the SimVascular web svMultiPhysics documentation because most users don't know about GitHub.