refactor: use createApp & app.use vue 3 API

Vue can no longer be imported from `vue`. Instead, we need to create
a vue app instance and "install" our components on the app.

src/main.ts

@@ -2,15 +2,12 @@ import VueImgix from '@/plugins/vue-imgix';
 import Vue from 'vue';
 import App from './App.vue';
 
-Vue.config.productionTip = false;
+const app = Vue.createApp(App);
 
-Vue.use(VueImgix, {
+app.use(
+  VueImgix, {
   domain: 'assets.imgix.net',
   defaultIxParams: {
     auto: 'format',
   },
-});
-
-new Vue({
-  render: (h) => h(App),
-}).$mount('#app');
+}).mount('#app');

src/plugins/vue-imgix/index.ts

@@ -1,17 +1,17 @@
-import _Vue from 'vue';
+import _App from './App.vue';
 import { IxPicture } from './ix-picture';
 import { IxSource } from './ix-source';
 import { IVueUseImgixOptions } from './types';
 import { initVueImgix, IxImg } from './vue-imgix';
 
 // Declare install function executed by Vue.use()
-export function install(Vue: typeof _Vue, options: IVueUseImgixOptions) {
+export function install(App: typeof _App, options: IVueUseImgixOptions) {
   if (install.installed) return;
   install.installed = true;
   initVueImgix(options);
-  Vue.component('ix-img', IxImg);
-  Vue.component('ix-picture', IxPicture);
-  Vue.component('ix-source', IxSource);
+  App.use('ix-img', IxImg);
+  App.use('ix-picture', IxPicture);
+  App.use('ix-source', IxSource);
 }
 install.installed = false;