In `AppLauncher`, added self._livestream >= 1 to the list of conditions
which can cause omni.kit.widget.toolbar to be loaded, as this extension
is loaded later based in AppLauncher startup to remove the 'stop'
button, and this will cause a crash if not omni.kit.widget.toolbar is
not already loaded.

This is reproducible by using any 'experience' without toolbar enabled
while having LIVESTREAM=1. An example is the `--headless` execution in
our 'Training with an RL Agent' tutorial:
`./orbit.sh -p source/standalone/workflows/sb3/train.py --task
Isaac-Cartpole-v0 --num_envs 64 --headless`

## Type of change

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applicable. -->

- Bug fix (non-breaking change which fixes an issue)

## Checklist

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

<!--
As you go through the checklist above, you can mark something as done by
putting an x character in it

For example,
- [x] I have done this task
- [ ] I have not done this task
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---------
Signed-off-by: AutonomousHansen <50837800+AutonomousHansen@users.noreply.github.com>
Co-authored-by: jsmith-bdai <142246516+jsmith-bdai@users.noreply.github.com>
Co-authored-by: Mayank Mittal <12863862+Mayankm96@users.noreply.github.com>