R2 docs (#937)

* add empty release notes

* add R2 config to the examples

Author: TomNicholas

docs/usage.md

@@ -59,7 +59,6 @@ that can access your data. Available ObjectStores are described in the [obstore
     from obspec_utils.registry import ObjectStoreRegistry
     from obstore.store import from_url
 
-
     from virtualizarr import open_virtual_dataset, open_virtual_mfdataset
     from virtualizarr.parsers import HDFParser
 
@@ -71,6 +70,35 @@ that can access your data. Available ObjectStores are described in the [obstore
 
     ```
 
+=== "R2"
+
+    ```python
+
+    import xarray as xr
+    from obstore.store import S3Store
+    from obspec_utils.registry import ObjectStoreRegistry
+
+    from virtualizarr import open_virtual_dataset, open_virtual_mfdataset
+    from virtualizarr.parsers import HDFParser
+
+    endpoint = "https://f0b62eebfbdde1133378bfe3958325f6.r2.cloudflarestorage.com"
+    access_key_id = "<access_key_id>"
+    secret_access_key = "<secret_access_key>"
+    path = "<path_to_files>"
+    scheme = "s3://"
+    bucket_name = "<bucket_name>"
+    bucket = f"{scheme}{bucket_name}"
+
+    # create anon s3 store
+    store = S3Store.from_url(f"{bucket}", endpoint=endpoint, skip_signature=True)
+
+    # create s3 store with aws-style credentials
+    store = S3Store.from_url(f"{bucket}", endpoint=endpoint, access_key_id=access_key_id, secret_access_key=secret_access_key)
+
+    registry = ObjectStoreRegistry({f"{bucket}": store})
+
+    ```
+
 === "HTTP"
 
     ```python