fix(package): update vue-property-decorator to version 8.4.2

Closes #162

Author: greenkeeper[bot]

package.json

@@ -25,7 +25,7 @@
   "dependencies": {
     "babel-plugin-transform-runtime": "6.23.0",
     "find-babel-config": "1.2.0",
-    "vue-property-decorator": "8.3.0"
+    "vue-property-decorator": "8.4.2"
   },
   "devDependencies": {
     "@babel/core": "7.8.7",