Optional config argument to pause training at the very beginning.

[luocfprime]

Is your feature request related to a problem? Please describe.

When using nerf/3dgs editing methods, the appearance of the scenes can change very rapidly in the first few iterations. It is reasonable to optionally pause the optimization process at the beginning and start it after the web viewer is loaded.

Describe the solution you'd like

Add an optional argument to set training_state = "paused".

Describe alternatives you've considered

Overwrite the __init__ function of Trainer through monkey patching to set training_state = "paused".

Additional context Add any other context or screenshots about the feature request here.