ICU-23091 Fix CI job for Java formatter to start in ICU4J root dir

Author: echeran

.github/workflows/icu4j.yml

@@ -87,7 +87,9 @@ jobs:
             ${{ runner.os }}-maven-
           lookup-only: true
       - name: Check Java style
-        run: mvn spotless:check || (echo "Style checker failed. Formatting changes can be applied by 'mvn spotless:apply'" && exit 1)
+        run: |
+          cd ic4j;
+          mvn spotless:check || (echo "Style checker failed. Formatting changes can be applied by 'mvn spotless:apply'" && exit 1)
 
   # ICU4J build and unit test using Maven
   # https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-java-with-maven

icu4j/pom.xml

@@ -469,6 +469,11 @@
           <artifactId>exec-maven-plugin</artifactId>
           <version>3.4.1</version>
         </plugin>
+        <!-- 
+          Spotless info:
+            - How to preview what `mvn spotless:apply` will do: https://github.com/diffplug/spotless/tree/main/plugin-maven#how-do-i-preview-what-mvn-spotlessapply-will-do
+            - Apply Spotless to specific files: https://github.com/diffplug/spotless/tree/main/plugin-maven#can-i-apply-spotless-to-specific-files
+        -->
         <plugin>
           <groupId>com.diffplug.spotless</groupId>
           <artifactId>spotless-maven-plugin</artifactId>