Update contributing guidelines

Author: ST-DDT

CONTRIBUTING.md

@@ -4,15 +4,23 @@ We definitely welcome your patches and contributions to gRPC-Spring-Boot-Starter
 
 If you are new to github, please start by reading [Pull Request howto](https://help.github.com/articles/about-pull-requests/)
 
-##Code Formatting
-Code formatting is enforced using the [Spotless](https://github.com/diffplug/spotless)
-Gradle plugin or Maven plugin. You can use `gradle spotlessJavaApply` or `mvn spotless:apply`
- to format new code. Formatter and import order settings for Eclipse are
-available in the repository under
-[extra/eclipse-formatter.xml](extra/eclipse/eclipse-formatter.xml)
-and [extra/eclipse.importorder](extra/eclipse/eclipse.importorder),
-respectively.
-
-For IntelliJ IDEA there's a
-[plugin](https://plugins.jetbrains.com/plugin/6546) you can use in conjunction with the
-Eclipse settings.
+## Code Formatting
+
+Code formatting is enforced using the [Spotless](https://github.com/diffplug/spotless) Gradle plugin.
+You can use `gradle spotlessJavaApply` (java only) or `gradle spotlessApply` (all files)
+to format new code. Please run this task before submitting your pull request.
+
+### Eclipse
+
+For the eclipse IDE we use the following formatter files:
+
+* [extra/eclipse-formatter.xml](extra/eclipse/eclipse-formatter.xml)
+* [extra/eclipse.importorder](extra/eclipse/eclipse.importorder)
+
+These will help you maintaing the files order, if you run the formatter from eclipse.
+There are slight differences to the `spotless` plugin so please run it before submitting your PR anyway.
+
+### IntelliJ IDEA
+
+For IntelliJ IDEA there's a [Eclipse Code Formatter plugin](https://plugins.jetbrains.com/plugin/6546) you can use in
+conjunction with the Eclipse setting files.