Add force-graph chart backend

[ivan-pi]

force-graph: https://github.com/vasturiano/force-graph?tab=readme-ov-file

The fpm-modules implementation can be found here (also MIT-licensed): https://github.com/davidpfister/fpm-modules/blob/master/src/layout/force.f90

[ivan-pi]

With this change, we should also deprecate the flag -M,--mermaid and switch to a named backend option like -c, --chart <dot|mermaid|force>.

[ivan-pi]

See also the latest options in fpm-modules described here: https://fortran-lang.discourse.group/t/visualizing-fortran-projects-with-fpm-create-stunning-module-dependency-charts/9838/26?u=ivanpribec