add docs create-storage-record option and artifact-metadata permission

Signed-off-by: Meredith Lancaster <malancas@github.com>

README.md

@@ -45,11 +45,15 @@ attest:
    permissions:
      id-token: write
      attestations: write
+     artifact-metadata: write
    ```
 
    The `id-token` permission gives the action the ability to mint the OIDC token
    necessary to request a Sigstore signing certificate. The `attestations`
    permission is necessary to persist the attestation.
+   The `artifact-metadata` permission is required to generate artifact
+   metadata storage records. If this permission is not included, the action
+   will continue without creating the record.
 
 1. Add the following to your workflow after your artifact has been built and
    your SBOM has been generated:
@@ -101,6 +105,12 @@ See [action.yml](action.yml)
     # the "subject-digest" parameter be specified. Defaults to false.
     push-to-registry:
 
+    # Whether to create a storage record for the artifact.
+    # Requires that push-to-registry is set to true.
+    # Requires that the "subject-name" parameter specify the fully-qualified
+    # image name. Defaults to true.
+    create-storage-record:
+
     # Whether to attach a list of generated attestations to the workflow run
     # summary page. Defaults to true.
     show-summary:
@@ -258,6 +268,10 @@ fully-qualified image name (e.g. "ghcr.io/user/app" or
 "acme.azurecr.io/user/app"). Do NOT include a tag as part of the image name --
 the specific image being attested is identified by the supplied digest.
 
+If the `push-to-registry` option is set to true, the Action will also
+emit an Artifact Metadata Storage Record. If you do not want to emit a
+storage record, set `create-storage-record` to `false`.
+
 > **NOTE**: When pushing to Docker Hub, please use "index.docker.io" as the
 > registry portion of the image name.