feat: add a warning for the working directory being root

src/main/java/io/kestra/plugin/gcp/runner/GcpBatchTaskRunner.java

@@ -51,6 +51,8 @@
         To use `inputFiles`, `outputFiles` or `namespaceFiles` properties, make sure to set the `bucket` property. The bucket serves as an intermediary storage layer for the task runner. Input and namespace files will be uploaded to the cloud storage bucket before the task run. Similarly, the task runner will store outputFiles in this bucket during the task run. In the end, the task runner will make those files available for download and preview from the UI by sending them to internal storage.
         To make it easier to track where all files are stored, the task runner will generate a folder for each task run. You can access that folder using the `{{bucketPath}}` Pebble expression or the `BUCKET_PATH` environment variable.
         
+        Warning, contrarily to other task runners, this task runner didn't run the task in the working directory but in the root directory. You must use the `{{workingDir}}` Pebble expression or the `WORKING_DIR` environment variable to access files.
+        
         Note that when the Kestra Worker running this task is terminated, the batch job will still run until completion."""
 )
 @Plugin(