chore(storage/v2): publish README with disclaimer

PiperOrigin-RevId: 569341227

google/storage/v2/storage_v2.yaml

@@ -13,7 +13,21 @@ enums:
 - name: google.storage.v2.ServiceConstants.Values
 
 documentation:
-  summary: 'Lets you store and retrieve potentially-large, immutable data objects.'
+  summary: |-
+    Stop. This folder is likely not what you are looking for.
+
+    This folder contains protocol buffer definitions for an unreleased API for
+    accessing Cloud Storage. Unless told otherwise by a Google Cloud
+    representative, do not use any of the contents of this folder. If you
+    would like to use Cloud Storage, please consult our [official
+    documentation](https://cloud.google.com/storage/docs/apis) for details on
+    our XML and JSON APIs, or else consider one of our
+    [client
+    libraries](https://cloud.google.com/storage/docs/reference/libraries).
+
+    This API defined in this folder is unreleased and may shut off, break, or
+    fail at any time for any users who are not registered as a part of a
+    private preview program.
   overview: |-
     The Google Cloud Storage API allows applications to read and write data
     through the abstractions of buckets and objects, which are similar to