refactor: make field final

src/main/java/com/github/cleydyr/maven/plugin/CompileSassMojo.java

@@ -37,7 +37,7 @@
 @Mojo(name = "compile-sass", defaultPhase = LifecyclePhase.PROCESS_RESOURCES, threadSafe = true)
 public class CompileSassMojo extends AbstractMojo {
 
-    private FileCounter fileCounter;
+    private final FileCounter fileCounter;
 
     protected SassCommandBuilder sassCommandBuilder;