add https://babeljs.io/docs/en/babel-plugin-proposal-optional-chaining

babel.config.js

@@ -26,6 +26,7 @@ module.exports = function(api) {
         },
       },
     ],
+    '@babel/plugin-proposal-optional-chaining',
     [
       '@babel/plugin-proposal-class-properties', { loose: true },
     ],

package.json

@@ -158,6 +158,7 @@
     "@atlaskit/navigation-next": "^8.0.2",
     "@babel/core": "^7.4.5",
     "@babel/plugin-proposal-class-properties": "^7.8.3",
+    "@babel/plugin-proposal-optional-chaining": "^7.9.0",
     "@babel/polyfill": "^7.4.4",
     "@babel/preset-env": "^7.4.5",
     "@babel/preset-react": "^7.0.0",

yarn.lock

@@ -688,6 +688,14 @@
     "@babel/helper-plugin-utils" "^7.0.0"
     "@babel/plugin-syntax-optional-catch-binding" "^7.2.0"
 
+"@babel/plugin-proposal-optional-chaining@^7.9.0":
+  version "7.9.0"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-optional-chaining/-/plugin-proposal-optional-chaining-7.9.0.tgz#31db16b154c39d6b8a645292472b98394c292a58"
+  integrity sha512-NDn5tu3tcv4W30jNhmc2hyD5c56G6cXx4TesJubhxrJeCvuuMpttxr0OnNCqbZGhFjLrg+NIhxxC+BK5F6yS3w==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.8.3"
+    "@babel/plugin-syntax-optional-chaining" "^7.8.0"
+
 "@babel/plugin-proposal-unicode-property-regex@^7.4.4":
   version "7.4.4"
   resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-unicode-property-regex/-/plugin-proposal-unicode-property-regex-7.4.4.tgz#501ffd9826c0b91da22690720722ac7cb1ca9c78"
@@ -739,6 +747,13 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.0.0"
 
+"@babel/plugin-syntax-optional-chaining@^7.8.0":
+  version "7.8.3"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-optional-chaining/-/plugin-syntax-optional-chaining-7.8.3.tgz#4f69c2ab95167e0180cd5336613f8c5788f7d48a"
+  integrity sha512-KoK9ErH1MBlCPxV0VANkXW2/dw4vlbGDrFgz8bmUsBGYkFRcbRwMh6cIJubdPrkxRwuGdtCk0v/wPTKbQgBjkg==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.8.0"
+
 "@babel/plugin-transform-arrow-functions@^7.2.0":
   version "7.2.0"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-arrow-functions/-/plugin-transform-arrow-functions-7.2.0.tgz#9aeafbe4d6ffc6563bf8f8372091628f00779550"