gulp: add French translation, update page (#10809)

* gulp: add French translation, update page

pages/common/gulp.md

@@ -1,7 +1,7 @@
 # gulp
 
 > JavaScript task runner and streaming build system.
-> Tasks are defined within gulpfile.js at the project root.
+> Tasks are defined within `gulpfile.js` at the project root.
 > More information: <https://github.com/gulpjs/gulp-cli>.
 
 - Run the default task:
@@ -11,3 +11,7 @@
 - Run individual tasks:
 
 `gulp {{task}} {{othertask}}`
+
+- Print the task dependency tree for the loaded gulpfile:
+
+`gulp --tasks`