docker: Added admin password change via env var

run.sh

 #!/usr/bin/env bash
 
-docker run --rm --detach --publish 8080:8080 code-elevator
+# admin password defaults to secret if corresponding env var not set
+: ${ADMIN_PASSWORD:=secret}
+
+docker run --rm --detach --publish 8080:8080 -e "JAVA_OPTIONS=-DADMIN_PASSWORD=$ADMIN_PASSWORD" code-elevator