Add support for addl stage-3 plugins

.babelrc.js

@@ -18,6 +18,7 @@ const plugins = [
   '@babel/plugin-syntax-import-meta',
   '@babel/plugin-proposal-class-properties',
   '@babel/plugin-proposal-json-strings',
+  '@babel/plugin-proposal-private-methods',
 ];
 
 // add code coverage tooling if necessary

package.json

@@ -22,6 +22,7 @@
     "@babel/core": "^7.2.2",
     "@babel/plugin-proposal-class-properties": "^7.2.3",
     "@babel/plugin-proposal-json-strings": "^7.2.0",
+    "@babel/plugin-proposal-private-methods": "^7.2.3",
     "@babel/plugin-syntax-dynamic-import": "^7.2.0",
     "@babel/plugin-syntax-import-meta": "^7.2.0",
     "@babel/preset-env": "^7.2.3",

yarn.lock

@@ -296,6 +296,14 @@
     "@babel/helper-plugin-utils" "^7.0.0"
     "@babel/plugin-syntax-optional-catch-binding" "^7.2.0"
 
+"@babel/plugin-proposal-private-methods@^7.2.3":
+  version "7.2.3"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-private-methods/-/plugin-proposal-private-methods-7.2.3.tgz#aff0f5436df2c4365938c0309d551984e42c290c"
+  integrity sha512-jehrt1/TuLdLeBAVEv1VmTCNJcvSj+5Ozp7l21DN19Ylo0ATxpZ5bDk8i4WS9Ngvdgk/YTcqJCTp3uY2lwQoxw==
+  dependencies:
+    "@babel/helper-create-class-features-plugin" "^7.2.3"
+    "@babel/helper-plugin-utils" "^7.0.0"
+
 "@babel/plugin-proposal-unicode-property-regex@^7.2.0":
   version "7.2.0"
   resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-unicode-property-regex/-/plugin-proposal-unicode-property-regex-7.2.0.tgz#abe7281fe46c95ddc143a65e5358647792039520"