docs(devguide): add missing app.module.js source in Basics > Forms (#2342)

Add missing app.module.js source example in Basics > Forms dev guide
- File is missing for JavaScript, but present for TypeScript

Author: pixelchutes

public/docs/js/latest/guide/forms.jade

@@ -636,6 +636,7 @@ figure.image-display
   `forms/js/app/hero-form.component.js,
    forms/js/app/hero-form.component.html,
    forms/js/app/hero.js,
+   forms/js/app/app.module.js,
    forms/js/app/app.component.js,
    forms/js/app/main.js,   
    forms/js/index.html,
@@ -644,6 +645,7 @@ figure.image-display
   `hero-form.component.js,
    hero-form.component.html,   
    hero.js,
+   app.module.js,
    app.component.js,
    main.js,
    index.html,