Merge pull request #57 from mackerelio/update-readme

Note: MariaDB is not supported

Author: yseto

README.md

@@ -21,3 +21,5 @@ command = "/path/to/mackerel-plugin-mysql"
 - `v1.3.0 >=` mysql 5.7, 8.0, 8.4 and above
 - `v1.1.0 >=` mysql 5.7, 8.0
 - `v1.0.0` mysql 5.0, 5.1, 5.5, 5.6, 5.7, 8.0
+
+Note: MariaDB is not supported.