docs: add link text

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

packages/noco-docs/docs/020.getting-started/050.self-hosted/020.environment-variables.md

@@ -51,7 +51,7 @@ For production use cases, it is **recommended** to set at least:
 | `NC_SMTP_USERNAME` | User name for authentication in SMTP plugin. | |
 | `NC_SMTP_PASSWORD` | User password for authentication in SMTP plugin. | |
 | `NC_SMTP_SECURE` | Enable secure authentication in SMTP plugin. Set to `true` to enable, any other value is treated as `false`. | |
-| `NC_SMTP_IGNORE_TLS` | Ignore TLS in SMTP plugin. Set to `true` to ignore TLS, any other value is treated as `false`. For more information, visit https://nodemailer.com/smtp/. | |
+| `NC_SMTP_IGNORE_TLS` | Ignore TLS in SMTP plugin. Set to `true` to ignore TLS, any other value is treated as `false`. For more information, visit [Nodemailer SMTP documentation](https://nodemailer.com/smtp/). | |
 | `NC_S3_BUCKET_NAME` | AWS S3 bucket name for S3 storage plugin. | |
 | `NC_S3_REGION` | AWS S3 region for S3 storage plugin. | |
 | `NC_S3_ACCESS_KEY` | AWS access key ID for S3 storage plugin. | |