feat(envs): add LIBERO-plus integration for evaluation benchmarks

Add LiberoPlusEnv config (subclass of LiberoEnv), register libero_plus
env type in factory, add import fallbacks for LIBERO-plus package
structure, and add libero_plus optional dependency group in pyproject.toml.

Made-with: Cursor

pyproject.toml

@@ -175,6 +175,11 @@ video_benchmark = ["scikit-image>=0.23.2,<0.26.0", "pandas>=2.2.2,<2.4.0"]
 aloha = ["gym-aloha>=0.1.2,<0.2.0", "lerobot[scipy-dep]"]
 pusht = ["gym-pusht>=0.1.5,<0.2.0", "pymunk>=6.6.0,<7.0.0"] # TODO: Fix pymunk version in gym-pusht instead
 libero = ["lerobot[transformers-dep]", "hf-libero>=0.1.3,<0.2.0; sys_platform == 'linux'", "lerobot[scipy-dep]"]
+libero_plus = [
+    "lerobot[transformers-dep]",
+    "libero @ git+https://github.com/sylvestf/LIBERO-plus.git@main ; sys_platform == 'linux'",
+    "lerobot[scipy-dep]",
+]
 metaworld = ["metaworld==3.0.0", "lerobot[scipy-dep]"]
 
 # All