Adds licenses folder to docker container (#387)

# Description

Adds licenses folder to docker container. previously it was included as
part of .dockerignore and not copied into the container.

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] 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
- [ ] 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

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.dockerignore

@@ -4,6 +4,8 @@
 .gitignore
 # ignore docs
 docs/
+# copy in licenses folder to the container
+!docs/licenses/
 # ignore logs
 **/logs/
 **/runs/