✨ feat: v3.0 to v2.1 (#68)

* feat: v2.1 to v2.0

* [DEV] update to filter new 3.0 fields

* feat: v21tov20 with filters and v30tov21

* fix: gemini-code-assist comments

* remove: global stat copy

* fix: rename root to output-path

* feat: v3.0->v2.1 fields filter

* align v30_to_v21 logic to v21_to_v30

* delete v21_to_v20 logic for this PR

* remove unused code

* update readme

---------

Co-authored-by: Tavish <tavish9.chen@gmail.com>

ds_version_convert/v30_to_v21/README.md

@@ -0,0 +1,17 @@
+# LeRobot Dataset v30 to v21
+
+## Get started
+
+1. Install v3.0 lerobot
+
+   ```bash
+   git clone https://github.com/huggingface/lerobot.git
+   pip install -e .
+   ```
+
+2. Run the converter:
+   ```bash
+   python convert_dataset_v30_to_v21.py \
+       --repo-id=your_id \
+       --root=your_local_dir
+   ```