Merge pull request #125 from Inform-Software/dependabot/maven/com.diffplug.spotless-spotless-maven-plugin-2.21.0

Bump spotless-maven-plugin from 2.20.0 to 2.21.0

Author: TobiX

pom.xml

@@ -161,7 +161,7 @@
       <plugin>
         <groupId>com.diffplug.spotless</groupId>
         <artifactId>spotless-maven-plugin</artifactId>
-        <version>2.20.0</version>
+        <version>2.21.0</version>
         <executions>
           <execution>
             <goals>