docs: filling in preRegistration hook info

docs/latest/extensions/lifecycle/pre-registration.md

@@ -1,12 +1,30 @@
 # Lifecylce Hook: preRegistration
 
 If an extension defines the `preRegistration` lifecycle hook, it is called
-before any modules are registered in the `ExtensionManager`.
+before any modules are registered in the `ExtensionManager`. This hook can be
+used to:
+
+- initialize 3rd party libraries
+- register event listeners
+- add or call services
+- add or call commands
+
+The `preRegistration` hook receives an object containing the
+`ExtensionManager`'s associated `ServicesManager`, `CommandsManager`, and any
+`configuration` that was provided with the extension at time of registration.
+
+_Example `preRegistration` hook implementation_
 
 ```js
 export default {
   id: 'MyExampleExtension',
 
+  /**
+   * @param {ServicesManager} servicesManager
+   * @param {CommandsManager} commandsManager
+   * @param {object} configuration
+   * @returns void
+   */
   preRegistration({ servicesManager, commandsManager, configuration }) {
     console.log('Wiring up important stuff.');