docs: update toc and components presentation

Author: Guillaume Chau

README.md

@@ -15,7 +15,10 @@ Blazing fast scrolling of any amount of data ([demo](https://akryum.github.io/vu
 
 - [Installation](#installation)
 - [Usage](#usage)
-- [Example](#example)
+  - [RecycleScroller](#recyclescroller)
+  - [DynamicScroller](#dynamicscroller)
+  - [DynamicScrollerItem](#dynamicscrolleritem)
+  - [IdState](#idstate)
 
 # Installation
 
@@ -82,6 +85,8 @@ There are several components provided by `vue-virtual-scroller`:
 
 [DynamicScrollerItem](#dynamicscrolleritem) must wrap each item in a DynamicScroller to handle size computations.
 
+[IdState](#idstate) is a mixin that ease the local state management in reused components inside a RecycleScroller.
+
 ## RecycleScroller
 
 It's a virtual scroller which only renders the visible items and reuse all the components and DOM trees as the user scrolls.