chore: add vue to peerDependencies (#396)

Author: haoqunjiang

package.json

@@ -42,6 +42,9 @@
     "url": "https://github.com/vuejs/vue-class-component/issues"
   },
   "homepage": "https://github.com/vuejs/vue-class-component#readme",
+  "peerDependencies": {
+    "vue": "^2.0.0"
+  },
   "devDependencies": {
     "@babel/core": "^7.7.7",
     "@babel/plugin-proposal-class-properties": "^7.7.4",