Merge pull request #43 from neziw/renovate/checkstyle-12.x

Update dependency checkstyle to v12.3.1

Author: neziw

build.gradle

@@ -15,7 +15,7 @@ java {
 }
 
 checkstyle {
-    toolVersion = "12.3.0"
+    toolVersion = "12.3.1"
     maxWarnings = 0
 }