Adds keyboard controls for camera viewport

[T-K-233]

Description

This PR introduces an option to control the camera viewport using the keyboard.

Previously, creating a ViewportCameraController disabled mouse interaction with the viewport. This happened because the controller subscribed to the app’s post-update event stream and continuously called sim.set_camera_view(...), overriding user input. This made viewing the simulation environment difficult.

To address this, a new register_keyboard_control option is added to ViewerCfg. When enabled, the user can navigate the camera with numpad shortcuts (full keybinding list is provided below).

Example usage:

# in train.py or play.py
 viewer_cfg = ViewerCfg(
     eye=(-3.0, 0.0, 1.0),  # default camera position w.r.t. the target
     lookat=(0.0, 0.0, 0.0),
     origin_type="asset_root",
     asset_name="robot",
+    register_keyboard_control=True,
 )
 camera_controller = ViewportCameraController(env.unwrapped, viewer_cfg)

Keybinding

Numpad Key	Function
Numpad 0	Default view
Numpad 1	Front view
Ctrl + Numpad 1	Back view
Numpad 3	Right-side view
Ctrl + Numpad 3	Left-side view
Numpad 7	Top view
Ctrl + Numpad 7	Bottom view
Numpad 8	Arc upward
Numpad 2	Arc downward
Numpad 4	Arc left
Numpad 6	Arc right
Numpad + (plus)	Push in
Numpad – (minus)	Pull out
Ctrl + Numpad 8	Pedestal up
Ctrl + Numpad 2	Pedestal down

Note to reviewers: I’m not sure which documentation section this change should go into—guidance is appreciated.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update (?)

Checklist

• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[Mayankm96]

I think it would make sense to stick to default viewport controls here as options: https://docs.omniverse.nvidia.com/usd/latest/common/keyboard_shortcuts.html#viewport-controls

Not all keyboards have numpads in there.

[ooctipus]

I agree with mayank it will be nice if it can stick to the same way how isaacsim uses keyboard control :)), Numpad can be optionally there as well, but my keyboard doesn't have a numpad and I'd like to use this functionality.

[Mayankm96]

If these values are changed, then are they reflected on the UI too?