add babel plugin

@@ -10,6 +10,8 @@ module.exports = {
     'transform-vue-jsx',
     '@babel/transform-async-to-generator',
     '@babel/proposal-object-rest-spread',
-    '@babel/syntax-dynamic-import'
+    '@babel/syntax-dynamic-import',
+    '@babel/plugin-proposal-optional-chaining',
+    '@babel/plugin-proposal-nullish-coalescing-operator'
   ]
 };

@@ -83,7 +83,9 @@
   },
   "devDependencies": {
     "@babel/core": "^7.2.0",
+    "@babel/plugin-proposal-nullish-coalescing-operator": "^7.4.4",
     "@babel/plugin-proposal-object-rest-spread": "^7.2.0",
+    "@babel/plugin-proposal-optional-chaining": "^7.6.0",
     "@babel/plugin-syntax-dynamic-import": "^7.2.0",
     "@babel/plugin-transform-async-to-generator": "^7.2.0",
     "@babel/plugin-transform-runtime": "^7.2.0",

@@ -300,6 +300,14 @@
     "@babel/helper-plugin-utils" "^7.0.0"
     "@babel/plugin-syntax-json-strings" "^7.2.0"
 
+"@babel/plugin-proposal-nullish-coalescing-operator@^7.4.4":
+  version "7.4.4"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-nullish-coalescing-operator/-/plugin-proposal-nullish-coalescing-operator-7.4.4.tgz#41c360d59481d88e0ce3a3f837df10121a769b39"
+  integrity sha512-Amph7Epui1Dh/xxUxS2+K22/MUi6+6JVTvy3P58tja3B6yKTSjwwx0/d83rF7551D6PVSSoplQb8GCwqec7HRw==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.0.0"
+    "@babel/plugin-syntax-nullish-coalescing-operator" "^7.2.0"
+
 "@babel/plugin-proposal-object-rest-spread@^7.2.0":
   version "7.2.0"
   resolved "http://npm.yohops.com/@babel%2fplugin-proposal-object-rest-spread/-/plugin-proposal-object-rest-spread-7.2.0.tgz#88f5fec3e7ad019014c97f7ee3c992f0adbf7fb8"
@@ -314,6 +322,14 @@
     "@babel/helper-plugin-utils" "^7.0.0"
     "@babel/plugin-syntax-optional-catch-binding" "^7.2.0"
 
+"@babel/plugin-proposal-optional-chaining@^7.6.0":
+  version "7.6.0"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-optional-chaining/-/plugin-proposal-optional-chaining-7.6.0.tgz#e9bf1f9b9ba10c77c033082da75f068389041af8"
+  integrity sha512-kj4gkZ6qUggkprRq3Uh5KP8XnE1MdIO0J7MhdDX8+rAbB6dJ2UrensGIS+0NPZAaaJ1Vr0PN6oLUgXMU1uMcSg==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.0.0"
+    "@babel/plugin-syntax-optional-chaining" "^7.2.0"
+
 "@babel/plugin-proposal-unicode-property-regex@^7.2.0":
   version "7.2.0"
   resolved "http://npm.yohops.com/@babel%2fplugin-proposal-unicode-property-regex/-/plugin-proposal-unicode-property-regex-7.2.0.tgz#abe7281fe46c95ddc143a65e5358647792039520"
@@ -340,6 +356,13 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.0.0"
 
+"@babel/plugin-syntax-nullish-coalescing-operator@^7.2.0":
+  version "7.2.0"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-nullish-coalescing-operator/-/plugin-syntax-nullish-coalescing-operator-7.2.0.tgz#f75083dfd5ade73e783db729bbd87e7b9efb7624"
+  integrity sha512-lRCEaKE+LTxDQtgbYajI04ddt6WW0WJq57xqkAZ+s11h4YgfRHhVA/Y2VhfPzzFD4qeLHWg32DMp9HooY4Kqlg==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.0.0"
+
 "@babel/plugin-syntax-object-rest-spread@^7.0.0", "@babel/plugin-syntax-object-rest-spread@^7.2.0":
   version "7.2.0"
   resolved "http://npm.yohops.com/@babel%2fplugin-syntax-object-rest-spread/-/plugin-syntax-object-rest-spread-7.2.0.tgz#3b7a3e733510c57e820b9142a6579ac8b0dfad2e"
@@ -352,6 +375,13 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.0.0"
 
+"@babel/plugin-syntax-optional-chaining@^7.2.0":
+  version "7.2.0"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-optional-chaining/-/plugin-syntax-optional-chaining-7.2.0.tgz#a59d6ae8c167e7608eaa443fda9fa8fa6bf21dff"
+  integrity sha512-HtGCtvp5Uq/jH/WNUPkK6b7rufnCPLLlDAFN7cmACoIjaOOiXxUt3SswU5loHqrhtqTsa/WoLQ1OQ1AGuZqaWA==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.0.0"
+
 "@babel/plugin-transform-arrow-functions@^7.2.0":
   version "7.2.0"
   resolved "http://npm.yohops.com/@babel%2fplugin-transform-arrow-functions/-/plugin-transform-arrow-functions-7.2.0.tgz#9aeafbe4d6ffc6563bf8f8372091628f00779550"