fix: 📝 Fixed sftp config readme

Added a detailed explanation inside the README for the sftpgo configuration, this contains an extra step for synology users.

templates/sftpgo/README.md

@@ -12,7 +12,7 @@ Usage:
 
 1. Import the compose file into Portainer's Stacks or App Templates.
 2. Configure the environment variables for the initial admin user and database settings.
-3. Map the data volume to persist user data and configuration.
+3. Map the data volume to persist user data and configuration. (See Extra Note)
 4. Deploy the stack via Portainer.
 5. Access the admin web interface at `http://<your-ip>:8080/web/admin`.
 
@@ -21,4 +21,16 @@ Helpful links:
 - GitHub Repository: https://github.com/drakkan/sftpgo
 - Documentation: https://github.com/drakkan/sftpgo/tree/main/docs
 
-**Status:** Ready for configuration
+Extra Note:
+Using a portainer install on a Synology Nas requires some extra folder permission configuration. You must give the data folder read and write permissions to everyone. This can be done with:
+
+1. Open **File Station** on your Synology NAS.
+2. Right-click the folder mapped to SFTPGo and select **Properties**.
+3. Go to the **Permission** tab.
+4. Click **Create** or **Edit** to add the `Everyone` group.
+5. Check **Read** and **Write** permissions.
+6. Check the box **Apply to this folder, sub-folders and files**.
+7. Click **Done** and **Save**.
+
+
+**Status:** Ready for configuration