Added some gulp info

Author: Felix Hennig

README.adoc

@@ -26,6 +26,12 @@ We have added our own tracking solution into `src/partials/head-scripts.hbs`. It
 === Highlight.js v10
 [Ticket](https://github.com/stackabletech/documentation/issues/232) - Due to the removal of HTML-passthru in v11 (which we need for [Callouts](https://docs.asciidoctor.org/asciidoc/latest/verbatim/callouts/)) the highlight.js has not been updated from v10. This also affects the Antora Default UI. Both decisions will be revisited when the upstream upgrade is available.
 
+=== Gulp
+
+To work on the build process of this, you need to understand [gulp](https://gulpjs.com/docs/en/getting-started/javascript-and-gulpfiles). Gulp is a builder/bundler that is used to package this antora UI.
+
+In this project, `gulpfile.js` is the main entrypoint for gulp. This file references tasks in the `gulp.d` directory.
+
 == Code of Conduct
 
 The Antora project and its project spaces are governed by our https://gitlab.com/antora/antora/-/blob/HEAD/CODE-OF-CONDUCT.adoc[Code of Conduct].