📚[DOC]: documentation for the backward compatibility of `Module`

[CharlelieLrt]

How would you describe the priority of this documentation request

Critical (currently preventing usage)

Is this for new documentation, or an update to existing docs?

New

Describe the incorrect/future/missing documentation

Problem

As noted by @nbren12 , PhysicsNeMo implements a Module versioning system that is at the core of the backward compatibility mechanism that allows to load and use older models implementations. However, this versioning system and the backward compatibility feature is not documented anywhere.

Solution

The documentation should explain to users who build their own models and training recipes how to leverage the versioning system to enable backward compatibility in their libraries.