docs: SetupContext.refs type, remove unnecessary docs (#611)

* Update README.md

* Fix type of SetupContext.ref

* Remove redundant docs

Author: subdavis

README.md

@@ -368,18 +368,6 @@ export default {
 }
 ```
 
-You may also need to augment the `SetupContext` when working with TypeScript:
-
-```ts
-import Vue from 'vue'
-
-declare module '@vue/composition-api' {
-  interface SetupContext {
-    readonly refs: { [key: string]: Vue | Element | Vue[] | Element[] }
-  }
-}
-```
-
 </details>
 
 ### Reactive

src/component/componentOptions.ts

@@ -1,4 +1,4 @@
-import { VNode, ComponentOptions as Vue2ComponentOptions } from 'vue'
+import Vue, { VNode, ComponentOptions as Vue2ComponentOptions } from 'vue'
 import { Data } from './common'
 import { ComponentPropsOptions, ExtractPropTypes } from './componentProps'
 import { ComponentInstance, ComponentRenderProxy } from './componentProxy'
@@ -25,7 +25,7 @@ export interface SetupContext {
   /**
    * @deprecated not avaliable in Vue 3
    */
-  readonly refs: Data
+  readonly refs: { [key: string]: Vue | Element | Vue[] | Element[] }
 
   emit(event: string, ...args: any[]): void
 }