[FEAT] PathResolver: improve the demo

[tbouffard]

Note: if needed, split this issue for better track changes and progression

Possible improvements

• add a way to load local diagram
• let choose to load diagram from a provided list of samples: could help to demonstrate special cases not covered by PathResolver(gateways and loop: [FEAT] CasePathResolver: handle "backward lonely edge" with exclusive gateways #14 and [FEAT] CasePathResolver: handle "forward lonely edge" from an exclusive gateway targeting a merge exclusive gateway #10)
• disable the "compute path" when no new elements have been selected or unselected (for instance, right after a computation)