feat: Compatible with vue3

Author: zhangzheng-zz

package.json

@@ -1,7 +1,7 @@
 {
   "name": "vue-clipboard2",
-  "version": "0.3.1",
-  "description": "A Vuejs2 binding for clipboard.js",
+  "version": "0.3.2",
+  "description": "A Vuejs2 & Vuejs3 binding for clipboard.js",
   "main": "vue-clipboard.js",
   "scripts": {
     "build": "$(npm bin)/eslint vue-clipboard.js && $(npm bin)/browserify browserify-me.js -o dist/vue-clipboard.js && $(npm bin)/uglifyjs dist/vue-clipboard.js -o dist/vue-clipboard.min.js && echo Success"

vue-clipboard.js

@@ -7,8 +7,9 @@ var VueClipboardConfig = {
 
 var VueClipboard = {
   install: function (Vue) {
-    Vue.prototype.$clipboardConfig = VueClipboardConfig
-    Vue.prototype.$copyText = function (text, container) {
+    var globalPrototype = Vue.version.slice(0, 2) === '3.' ? Vue.config.globalProperties : Vue.prototype
+    globalPrototype.$clipboardConfig = VueClipboardConfig
+    globalPrototype.$copyText = function (text, container) {
       return new Promise(function (resolve, reject) {
         var fakeElement = document.createElement('button')
         var clipboard = new Clipboard(fakeElement, {