first implementation

frontend/node_modules/vue-demi/scripts/postinstall.js

@@ -0,0 +1,19 @@
+const { switchVersion, loadModule } = require('./utils')
+
+const Vue = loadModule('vue')
+
+if (!Vue || typeof Vue.version !== 'string') {
+  console.warn('[vue-demi] Vue is not found. Please run "npm install vue" to install.')
+}
+else if (Vue.version.startsWith('2.7.')) {
+  switchVersion(2.7)
+}
+else if (Vue.version.startsWith('2.')) {
+  switchVersion(2)
+}
+else if (Vue.version.startsWith('3.')) {
+  switchVersion(3)
+}
+else {
+  console.warn(`[vue-demi] Vue version v${Vue.version} is not supported.`)
+}