added gradle mjml plugin to documentation (#2735)

doc/tooling.md

@@ -26,6 +26,10 @@ In addition to the language plugin, a linter is available to highlight errors in
 
 [IntelliJ IDEA](https://www.jetbrains.com/idea/) is an IDE developed by JetBrains. The plugin provides you with a (near) realtime preview, auto complete, inline documentation and code analysis. Its available on the [JetBrains Marketplace](https://plugins.jetbrains.com/plugin/16418-mjml-support).
 
+## Gradle Plugin - MJML Compilation
+[Gradle](https://gradle.org/) is a build tool for a various set of languages and environments, mainly used for java/kotlin. The plugin provides an easy way to embed your mjml templates to your java/kotlin application in its resources in precompiled form (html). 
+It's available through the gradle plugin system [io.freefair.mjml.java](https://plugins.gradle.org/plugin/io.freefair.mjml.java) and documentation is available here [FreeFair User Guide](https://docs.freefair.io/gradle-plugins/current/reference/)
+
 ## Gulp
 
 Gulp is a tool designed to help you automate and enhance your workflow. Our plugin enables you to plug the MJML translation engine into your workflow, helping you to streamline your development workflow. It is available here on [Github](https://github.com/mjmlio/gulp-mjml)