docs: update docs

Author: hunterliu1003

packages/docs/content/2.get-started/1.guide/2.concepts.md renamed to packages/docs/content/2.get-started/1.guide/1.concepts.md

@@ -2,6 +2,10 @@
 
 These are the core concepts you need to know about vue-final-modal and its approach to modals management.
 
+::alert{type=danger}
+❗️ If you came from vue-final-modal 3.x, please check the [migration guide](/get-started/guide/migration-guide).
+::
+
 ## What is VueFinalModal?
 
 `vue-final-modal` is a modal library built specifically for Vue.js and as such it makes some assumptions and enforces "best-practices" for your modals while being versatile and customizable.
@@ -17,6 +21,8 @@ These are the core concepts you need to know about vue-final-modal and its appro
   - Full control to the zIndex of the nested modals (see [zIndexFn prop](/api/components/vue-final-modal#zindexfn)).
   - Customizable `<Transition>` for the modal content and overlay.
   - Provide Higher order components including [VFullscreen](/api/components/v-fullscreen) and [VBottomSheet](/api/components/v-bottom-sheet).
+  - Fully tree-shakable! Only what you use will get imported.
+  - Tiny footprint! Only 4.x kB! Vue Final Modal focuses on the core functionality of modals, leaves the complex CSS up to the developer.
 ::
 
 ### A Styleless component

packages/docs/content/2.get-started/1.guide/3.setup.md renamed to packages/docs/content/2.get-started/1.guide/2.setup.md

@@ -2,6 +2,10 @@
 
 How to start with Vue Final Modal, by creating a fresh new project or adding it to your Vue application.
 
+::alert{type=danger}
+❗️ If you came from vue-final-modal 3.x, please check the [migration guide](/get-started/guide/migration-guide).
+::
+
 ## Installation
 
 ::code-group