fix: add healthcheck test command, fixes #29 (#30)

Author: coolbrewed

docker-compose.phpmyadmin.yaml

@@ -23,6 +23,7 @@ services:
       - HTTP_EXPOSE=8036:80
       - HTTPS_EXPOSE=8037:80
     healthcheck:
+      test: ["CMD-SHELL", "true"]
       interval: 120s
       timeout: 2s
       retries: 1