Bump com.diffplug.spotless:spotless-maven-plugin from 3.2.1 to 3.6.0 (#89)

Author: dependabot[bot]

pom.xml

@@ -58,7 +58,7 @@
       <plugin>
         <groupId>com.diffplug.spotless</groupId>
         <artifactId>spotless-maven-plugin</artifactId>
-        <version>3.2.1</version>
+        <version>3.6.0</version>
         <executions>
           <execution>
             <id>spotless-java</id>