chore: add migration guide for 3.0 (#2130)

Author: reesscot

docs/src/pages/[platform]/components/icon/react.mdx

@@ -42,9 +42,10 @@ Import the Icon component and styles.
 <Alert variation="warning" heading="Deprecated">
   The built-in icons were removed in version `3.0`. You can use the
   [react-icons](https://react-icons.github.io/react-icons) package or other
-  `import {ICON_NAME} from
-  '@aws-amplify/ui-react';` becomes `import {ICON_NAME} from 'react-icons/md';`
   React icon libraries in its place. 
+
+  `import {ICON_NAME} from '@aws-amplify/ui-react';` => `import {ICON_NAME} from 'react-icons/md';`
+
 </Alert>
 
 ## Custom icon

docs/src/pages/[platform]/getting-started/migration/migration.react.mdx

@@ -1,21 +1,62 @@
 import { Tabs, TabItem } from '@aws-amplify/ui-react';
 import { Alert } from '@aws-amplify/ui-react';
 
-## Installation
+## 2.x to 3.x
 
-Install the latest version of the `@aws-amplify/ui-react` library.
+### Installation
+Install the 3.x version of the `@aws-amplify/ui-react` library.
 
 <Tabs>
 <TabItem title="npm">
 
 ```shell
-npm install aws-amplify @aws-amplify/ui-react@latest
+npm install aws-amplify @aws-amplify/ui-react@3.x
 ```
 
 </TabItem>
 <TabItem title="yarn">
 ```shell
-yarn add aws-amplify @aws-amplify/ui-react@latest
+yarn add aws-amplify @aws-amplify/[email protected]
+```
+
+</TabItem>
+</Tabs>
+
+### Update and usage
+
+The following breaking changes where introduced in `@aws-amplify/ui-react` major version `3.0`:
+
+#### 1. We removed the built-in icons (Icon360, IconSave, etc).
+
+Replace any icon components in use the react-icons package or other React icon libraries in its place.
+
+```diff
+- import { IconSave } from '@aws-amplify/ui-react';
++ import { MdSave } from 'react-icons/md';
+```
+
+Note: We did not remove the [Icon](/react/components/icon) component, which allows customers to easily add SVG icons using the `pathData` prop.
+
+#### 2. We removed `ShareText` export.
+
+This export has been removed and should no longer be used.
+
+## 1.x to 2.x
+### Installation
+
+Install the 2.x version of the `@aws-amplify/ui-react` library.
+
+<Tabs>
+<TabItem title="npm">
+
+```shell
+npm install aws-amplify @aws-amplify/[email protected]
+```
+
+</TabItem>
+<TabItem title="yarn">
+```shell
+yarn add aws-amplify @aws-amplify/[email protected]
 ```
 
 </TabItem>