feat: add iframe whitelist domain env var for on-premise deployments

Author: DarkPhoenix2704

content/self-hosting/environment-variables.mdx

@@ -109,7 +109,7 @@ To update **either** `NC_ADMIN_EMAIL` or `NC_ADMIN_PASSWORD`, you must set **bot
 | `NC_MIGRATIONS_DISABLED`             | No        | Disables NocoDB migrations.                                                                                                                                                                           |                                            |
 | `NC_DISABLE_AUDIT`                   | No        | Disables the audit log feature.                                                                                                                                                                       | Defaults to `false`.                       |
 | `NC_AUTOMATION_LOG_LEVEL`            | No        | Configures logging levels for automation features. Possible values: `OFF`, `ERROR`, `ALL`. More details can be found under [Webhooks](/docs/product-docs/automation/webhook/create-webhook).                            | Defaults to `OFF`.                         |
-
+| `NC_IFRAME_WHITELIST_DOMAINS`        | No        | Comma-separated list of domains allowed to be embedded in iframes. (Only available in NocoDB On-premise) eg: `*.nocodb.com,*.mycompany.com`                                                                                       |                                            |
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