Add supported platforms

Author: technicalguru

README.md

@@ -15,6 +15,10 @@ The following versions are available from DockerHub. The image tag matches the P
 
 * [2.11.0.10, 2.11.0, 2.11, 2, latest](https://github.com/technicalguru/docker-mailserver-opendkim/tree/v2.11.0.10) - [Dockerfile](https://github.com/technicalguru/docker-mailserver-opendkim/blob/2.11.0.10/Dockerfile)
 
+# Supported Platforms
+* linux/amd64
+* linux/arm64
+
 # Features
 * Bootstrap from scratch: See more information below.
 * DKIM signing and verification