pyproject: add sigstore-models

Author: woodruffw

pyproject.toml

@@ -37,6 +37,9 @@ dependencies = [
   "rich >= 13,< 15",
   "rfc8785 ~= 0.1.2",
   "rfc3161-client >= 1.0.3,< 1.1.0",
+  # Both sigstore-models and sigstore-rekor types are unstable
+  # so we pin them conservatively.
+  "sigstore-models == 0.0.1",
   "sigstore-rekor-types == 0.0.18",
   "tuf ~= 6.0",
   "platformdirs ~= 4.2",