[FEAT] Move Legacy code into a legacy directory

legacy/frontend/score/src/main.js

@@ -0,0 +1,11 @@
+import '@babel/polyfill'
+import 'mutationobserver-shim'
+import Vue from 'vue'
+import './plugins/bootstrap-vue'
+import App from './App.vue'
+
+Vue.config.productionTip = false
+
+new Vue({
+  render: h => h(App),
+}).$mount('#app')