chore(nodejs): update client ref docs link in metadata (#360)

.repo-metadata.json

@@ -4,5 +4,6 @@
   "release_level": "ga",
   "language": "nodejs",
   "repo": "googleapis/google-p12-pem",
-  "distribution_name": "google-p12-pem"
+  "distribution_name": "google-p12-pem",
+  "client_documentation": "https://cloud.google.com/nodejs/docs/reference/google-p12-pem/latest"
 }

README.md

@@ -17,7 +17,7 @@ Convert Google .p12 keys to .pem keys.
 A comprehensive list of changes in each version may be found in
 [the CHANGELOG](https://github.com/googleapis/google-p12-pem/blob/master/CHANGELOG.md).
 
-
+* [google-p12-pem Node.js Client API Reference][client-docs]
 
 * [github.com/googleapis/google-p12-pem](https://github.com/googleapis/google-p12-pem)
 
@@ -85,6 +85,9 @@ Samples are in the [`samples/`](https://github.com/googleapis/google-p12-pem/tre
 
 
 
+The [google-p12-pem Node.js Client API Reference][client-docs] documentation
+also contains samples.
+
 ## Supported Node.js Versions
 
 Our client libraries follow the [Node.js release schedule](https://nodejs.org/en/about/releases/).
@@ -141,7 +144,7 @@ Apache Version 2.0
 
 See [LICENSE](https://github.com/googleapis/google-p12-pem/blob/master/LICENSE)
 
-
+[client-docs]: https://cloud.google.com/nodejs/docs/reference/google-p12-pem/latest
 
 [shell_img]: https://gstatic.com/cloudssh/images/open-btn.png
 [projects]: https://console.cloud.google.com/project