ci: configure dependabot to monitor maven-clean-plugin updates

Part of #1590

Author: php-coder

.github/dependabot.yml

@@ -13,6 +13,7 @@ updates:
       - dependency-name: "org.apache.commons:commons-lang3"
       - dependency-name: "org.apache.commons:commons-text"
       - dependency-name: "org.apache.maven.plugins:maven-compiler-plugin"
+      - dependency-name: "org.apache.maven.plugins:maven-clean-plugin"
       - dependency-name: "org.apache.maven.plugins:maven-enforcer-plugin"
       - dependency-name: "org.apache.maven.plugins:maven-resources-plugin"
       - dependency-name: "org.apache.maven.plugins:maven-war-plugin"