✨ add version convert collections (#63)

* v20 to v21

* v21 to v20

* v21 to v30

* v16 to v20

* update dataset version convert readme

* update readme

ds_version_convert/v20_to_v21/README.md

@@ -0,0 +1,20 @@
+# LeRobot Dataset v20 to v21
+
+## Get started
+
+1. Install v2.1 lerobot
+    ```bash
+    git clone https://github.com/huggingface/lerobot.git
+    git checkout d602e8169cbad9e93a4a3b3ee1dd8b332af7ebf8
+    pip install -e .
+    ```
+
+2. Run the converter:
+    ```bash
+    python convert_dataset_v20_to_v21.py \
+        --repo-id=your_id \
+        --root=your_local_dir \
+        --delete-old-stats \
+        --push-to-hub \
+        --num-workers=8
+    ```