Adds babel plugin

Author: xcambar

package.json

@@ -21,6 +21,7 @@
     "test:all": "ember try:each"
   },
   "dependencies": {
+    "@babel/plugin-proposal-class-properties": "^7.5.5",
     "broccoli-rollup": "^4.1.1",
     "ember-cli-babel": "^7.7.3",
     "ember-get-config": "^0.2.4",

yarn.lock

@@ -239,7 +239,7 @@
     "@babel/helper-remap-async-to-generator" "^7.1.0"
     "@babel/plugin-syntax-async-generators" "^7.2.0"
 
-"@babel/plugin-proposal-class-properties@^7.1.0", "@babel/plugin-proposal-class-properties@^7.3.4":
+"@babel/plugin-proposal-class-properties@^7.1.0", "@babel/plugin-proposal-class-properties@^7.3.4", "@babel/plugin-proposal-class-properties@^7.5.5":
   version "7.5.5"
   resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-class-properties/-/plugin-proposal-class-properties-7.5.5.tgz#a974cfae1e37c3110e71f3c6a2e48b8e71958cd4"
   integrity sha512-AF79FsnWFxjlaosgdi421vmYG6/jg79bVD0dpD44QdgobzHKuLZ6S3vl8la9qIeSwGi8i1fS0O1mfuDAAdo1/A==