add docfor static js and css resource registry

Author: toalba

docs/classic-ui/static-resources.md

@@ -15,12 +15,80 @@ We often want to ship a website with a static resource, such as an image, icon,
 For this, we need to register static resources.
 
 
+## Registering javascript and css
+
+To register a static resource in Plone 6, we need to use the `plone.base.interfaces.resources.IBundleRegistry` interface.
+
+The following example registers a Javascript resource in `browser/profiles/default/registry` of your Plone 6 project.
+The js files have to be in the `browser/static` folder of your Plone 6 project.
+
+```xml
+<registry>
+  <records interface="plone.base.interfaces.resources.IBundleRegistry" prefix="plone.bundles/jscript">
+    <value key="enabled">True</value>
+    <value key="jscompilation">++plone++myproject.site/javascript.min.js</value>
+    <value key="load_async">False</value> 
+    <value key="load_defer">False</value>
+    <value key="depends">plone</value>
+  </records>
+</registry>
+```
+
+You can register a CSS resource in the same way.
+  
+  ```xml 
+  <registry>
+    <records interface="plone.base.interfaces.resources.IBundleRegistry" prefix="plone.bundles/css">
+      <value key="enabled">True</value>
+      <value key="csscompilation">++plone++myproject.site/style.min.css</value>
+      <value key="jscompilation">++plone++myproject.site/javascript.min.js</value>
+      <value key="load_async">False</value> 
+      <value key="load_defer">False</value>
+      <value key="depends">plone</value>
+    </records>
+  </registry>
+  ```
+
+Registering a js file and a css file in the same bundle is also possible.
+
+```xml
+    <registry>
+    <records interface="plone.base.interfaces.resources.IBundleRegistry" prefix="plone.bundles/css">
+      <value key="enabled">True</value>
+      <value key="csscompilation">++plone++myproject.site/style.min.css</value>
+      <value key="depends">plone</value>
+    </records>
+  </registry>
+```
+
+
 (classic-ui-static-resources-available-attributeslabel)=
 
 ## Available attributes
 
+The following attributes are available for registering a static resource:
+
+`enabled`
+:  Whether the bundle is enabled or not. If it is disabled, the bundle will not be loaded.
+
+`jscompilation`
+:  The path to the compiled js file.
+
+`csscompilation`
+:  The path to the compiled css file.
+
+`depends`
+:  A list of bundles that this bundle depends on.
+
+`load_async`
+:  Whether the bundle should be loaded asynchronously or not. *Only JS*
+
+`load_defer`
+:  Whether the bundle should be loaded deferred or not. *Only JS*
+
 
 (classic-ui-static-resources-loading-order-label)=
 
 ## Loading order of resources
 
+`depends` is used to define the loading order of resources, by specifying the name of the depending bundle.