add initial FAQ for BQ OAuth related to Google Drive scope (#4310)

## What are you changing in this pull request and why?
The BigQuery OAuth application requires some scopes to access Google
Drive files. This is adding a quick FAQ to the bottom of the page in
order to clarify why this is needed as part of the BQ OAuth connection
and links to external docs from the Google team.

## Checklist
- [ ] Review the [Content style
guide](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/content-style-guide.md)
and [About
versioning](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#adding-a-new-version)
so my content adheres to these guidelines.
- [ ] Needs a technical review from the adapter team as a second
opintion

website/docs/docs/cloud/manage-access/set-up-bigquery-oauth.md

@@ -74,3 +74,7 @@ You will then be redirected to BigQuery and asked to approve the drive, cloud pl
 <Lightbox src="/img/docs/dbt-cloud/using-dbt-cloud/dbt-cloud-enterprise/BQ-auth/BQ-access.png" title="BigQuery access request" />
 
 Select **Allow**. This redirects you back to dbt Cloud. You should now be an authenticated BigQuery user, ready to use the dbt Cloud IDE.
+
+## FAQs
+
+<FAQ path="Warehouse/bg-oauth-drive-scope"/>

website/docs/faqs/Warehouse/bq-oauth-drive-scope.md

@@ -0,0 +1,8 @@
+---
+title: Why does the BigQuery OAuth application require scopes to Google Drive?
+description: "Learn more about Google Drive scopes in the BigQuery OAuth application"
+sidebar_label: "BigQuery OAuth Drive Scopes"
+id: bq-oauth-drive-scope
+---
+
+BigQuery supports external tables over both personal Google Drive files and shared files. For more information, refer to [Create Google Drive external tables](https://cloud.google.com/bigquery/docs/external-data-drive).