feat: export version as named export

Author: yyx990803

Diff for: src/core/index.ts

@@ -2,6 +2,7 @@ import Vue from './instance/index'
 import { initGlobalAPI } from './global-api/index'
 import { isServerRendering } from 'core/util/env'
 import { FunctionalRenderContext } from 'core/vdom/create-functional-component'
+import { version } from 'v3'
 
 initGlobalAPI(Vue)
 
@@ -21,6 +22,6 @@ Object.defineProperty(Vue, 'FunctionalRenderContext', {
   value: FunctionalRenderContext
 })
 
-Vue.version = '__VERSION__'
+Vue.version = version
 
 export default Vue

Diff for: src/v3/index.ts

@@ -1,3 +1,5 @@
+export const version: string = '__VERSION__'
+
 export {
   ref,
   shallowRef,