fix: esm import bug

[SoonIter]

Fix the esm bundle bug of vue in "vue-grid-layout@3.0.0-beta1"

Failed to resolve component: grid-item at <App>
Failed to resolve component: grid-layout at <App>

import { GridItem, GridLayout } from "vue-grid-layout"; // undefined undefined

import { App } from 'vue';

import GridItem from './GridItem.vue';
import GridLayout from './GridLayout.vue';

export { GridLayout, GridItem };  // not work
 
const install = (app: App) => {
    app.component('grid-layout', GridLayout)
    app.component('grid-item', GridItem)
}
+install.GridItem = GridItem;
+install.GridLayout = GridLayout;

export default install;