chore: add enumeration data type to .repo-metadata.json (#246)

Adds a standard enumeration of library types in .repo-metadata.json

.repo-metadata.json

@@ -1,15 +1,16 @@
 {
-  "name": "workflows",
-  "name_pretty": "Cloud Workflows",
-  "product_documentation": "https://cloud.google.com/workflows",
-  "api_description": "allows you to ochestrate and automate Google Cloud and HTTP-based API services with serverless workflows.",
-  "client_documentation": "https://googleapis.dev/java/google-cloud-workflows/latest/index.html",
-  "release_level": "beta",
-  "transport": "grpc",
-  "language": "java",
-  "repo": "googleapis/java-workflows",
-  "repo_short": "java-workflows",
-  "distribution_name": "com.google.cloud:google-cloud-workflows",
-  "api_id": "workflows.googleapis.com",
-  "requires_billing": true
-}
+    "name": "workflows",
+    "name_pretty": "Cloud Workflows",
+    "product_documentation": "https://cloud.google.com/workflows",
+    "api_description": "allows you to ochestrate and automate Google Cloud and HTTP-based API services with serverless workflows.",
+    "client_documentation": "https://googleapis.dev/java/google-cloud-workflows/latest/index.html",
+    "release_level": "beta",
+    "transport": "grpc",
+    "language": "java",
+    "repo": "googleapis/java-workflows",
+    "repo_short": "java-workflows",
+    "distribution_name": "com.google.cloud:google-cloud-workflows",
+    "api_id": "workflows.googleapis.com",
+    "requires_billing": true,
+    "library_type": "GAPIC_AUTO"
+}