chore(librarian): onboard to librarian

.librarian/state.yaml

@@ -0,0 +1,10 @@
+image: us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/python-librarian-generator@sha256:c8612d3fffb3f6a32353b2d1abd16b61e87811866f7ec9d65b59b02eb452a620
+libraries:
+  - id: sqlalchemy-bigquery
+    version: 1.16.0
+    apis: []
+    source_roots:
+      - .
+    preserve_regex: []
+    remove_regex: []
+    tag_format: v{version}