Add script templates

[elementbound]

:sparkles: Description

When building new components, it would be useful to have some bootstrap code to work from, instead of having to start from scratch.

Use case

Users could choose script templates when creating new scripts, improving productivity.

Distribution

If possible, each addon should ship its own script templates. If not, they should all be shipped as part of netfox.extras

Notes

Candidates for script templates:

• CharacterBody3D for movement with rollback
• BaseNetInput with empty method impls
• BaseNetInput with a simple movement + jump tracker
• ❓ CharacterBody3D for movement with predictive synchronizer ( see #374 )
• ❓ CharacterBody2D equivalents

See #448

[albertok]

I'll include my RigidBody synchronizer