docs: add remote model requirements (#333)

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:
- [ ] Make sure to open an issue as a [bug/issue](https://togithub.com/googleapis/python-bigquery-dataframes/issues/new/choose) before writing your code!  That way we can discuss the change, evaluate designs, and agree on the general idea
- [ ] Ensure the tests and linter pass
- [ ] Code coverage does not decrease (if any source code was changed)
- [ ] Appropriate docs were updated (if necessary)

Fixes #320775961 🦕

Author: GarrettWu

README.rst

@@ -309,6 +309,23 @@ following IAM roles:
 * Storage Object Viewer (roles/storage.objectViewer)
 * Project IAM Admin (roles/resourcemanager.projectIamAdmin)
 
+To use BigQuery DataFrames ML remote models(bigframes.ml.remote or bigframes.ml.llm), you must enable the following APIs:
+
+* The BigQuery API (bigquery.googleapis.com)
+* The BigQuery Connection API (bigqueryconnection.googleapis.com)
+* The Vertex AI API (aiplatform.googleapis.com)
+
+To use BigQuery DataFrames ML remote models(bigframes.ml.remote or bigframes.ml.llm), you must be granted the
+following IAM roles:
+
+* BigQuery Data Editor (roles/bigquery.dataEditor)
+* BigQuery Connection Admin (roles/bigquery.connectionAdmin)
+* Service Account User (roles/iam.serviceAccountUser) on the
+  `service account <https://cloud.google.com/functions/docs/reference/iam/roles#additional-configuration>`__
+  ``[email protected]``
+* Vertex AI User (roles/aiplatform.user)
+* Project IAM Admin (roles/resourcemanager.projectIamAdmin)
+
 **Limitations**
 
 * Remote functions take about 90 seconds to become available when you first create them.