[ADD] developer: add a reference page on hooks (js)

closes odoo/documentation#1208

Signed-off-by: Géry Debongnie (ged) <ged@openerp.com>

content/developer/reference/javascript.rst

@@ -13,6 +13,7 @@ Javascript
     javascript/registries
     javascript/services
     javascript/generic_components
+    javascript/hooks
     javascript/javascript_cheatsheet
     javascript/javascript_reference
     javascript/mobile

content/developer/reference/javascript/hooks.rst

@@ -0,0 +1,49 @@
+=====
+Hooks
+=====
+
+`Owl hooks <https://github.com/odoo/owl/blob/master/doc/reference/hooks.md>`_ are a
+way to factorize code, even if it depends on some component lifecycle. Most hooks
+provided by Owl are related to the lifecycle of a component, but some of them (such as 
+`useComponent <https://github.com/odoo/owl/blob/master/doc/reference/hooks.md#usecomponent>`_)
+provide a way to build specific hooks.
+
+Using these hooks, it is possible to build many customized hooks that help solve
+a specific problem, or make some common tasks easier. The rest of this page
+documents the list of hooks provided by the Odoo web framework.
+
+useBus
+======
+
+Location
+--------
+
+`@web/core/utils/hooks`
+
+Description
+-----------
+
+Add and clear an event listener to a bus. This hook ensures that
+the listener is properly cleared when the component is unmounted.
+
+.. code-block:: javascript
+
+    import { useBus } from "@web/core/utils/hooks";
+
+    class MyComponent {
+      setup() {
+        useBus(this.env.bus, "some-event", event => {
+          console.log(event);
+        });
+      }
+    }
+
+API
+---
+
+.. js:function:: useBus(bus, eventName, callback)
+
+    :param EventBus bus: the target event bus
+    :param string eventName: the name of the event that we want to listen to
+    :param function callback: listener callback
+