feat: Add on mode init hook (#3882)

platform/docs/docs/platform/modes/lifecycle.md

@@ -9,9 +9,18 @@ sidebar_label: Lifecycle Hooks
 
 Currently, there are two hooks that are called for modes:
 
+- onModeInit
 - onModeEnter
 - onModeExit
 
+## onModeInit
+
+This hook gets run before the defined route has been entered by the mode. This
+hook can be used for initialization before the first render.
+
+This is called before `onModeEnter` calls. This allows modes to add or activate their own
+data sources and configuration before entering the mode (pre registrations).
+
 ## onModeEnter
 
 This hook gets run after the defined route has been entered by the mode. This