chore(storybook): update Babel config to suppress warning

See rails/webpacker#3008 (comment)

babel.config.js

@@ -1,4 +1,8 @@
 module.exports = {
   presets: ['@babel/preset-env', '@babel/preset-react', '@babel/preset-typescript'],
-  plugins: [['@babel/plugin-transform-class-properties', { loose: true }]]
+  plugins: [
+    ['@babel/plugin-transform-class-properties', { loose: true }],
+    ['@babel/plugin-proposal-private-methods', { loose: true }],
+    ['@babel/plugin-proposal-private-property-in-object', { loose: true }]
+  ]
 }

package.json

@@ -42,6 +42,8 @@
   "devDependencies": {
     "@babel/core": "^7.16.0",
     "@babel/plugin-proposal-class-properties": "^7.18.6",
+    "@babel/plugin-proposal-private-methods": "^7.18.6",
+    "@babel/plugin-proposal-private-property-in-object": "^7.21.11",
     "@babel/preset-env": "^7.16.4",
     "@babel/preset-react": "^7.16.0",
     "@babel/preset-typescript": "^7.16.0",

yarn.lock

@@ -518,9 +518,9 @@
     "@babel/helper-skip-transparent-expression-wrappers" "^7.20.0"
     "@babel/plugin-syntax-optional-chaining" "^7.8.3"
 
-"@babel/plugin-proposal-private-methods@^7.12.1":
+"@babel/plugin-proposal-private-methods@^7.12.1", "@babel/plugin-proposal-private-methods@^7.18.6":
   version "7.18.6"
-  resolved "https://registry.npmjs.org/@babel/plugin-proposal-private-methods/-/plugin-proposal-private-methods-7.18.6.tgz"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-private-methods/-/plugin-proposal-private-methods-7.18.6.tgz#5209de7d213457548a98436fa2882f52f4be6bea"
   integrity sha512-nutsvktDItsNn4rpGItSNV2sz1XwS+nfU0Rg8aCx3W3NOKVzdMjJRu0O5OkgDp3ZGICSTbgRpxZoWsxoKRvbeA==
   dependencies:
     "@babel/helper-create-class-features-plugin" "^7.18.6"
@@ -541,6 +541,16 @@
     "@babel/helper-plugin-utils" "^7.20.2"
     "@babel/plugin-syntax-private-property-in-object" "^7.14.5"
 
+"@babel/plugin-proposal-private-property-in-object@^7.21.11":
+  version "7.21.11"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-private-property-in-object/-/plugin-proposal-private-property-in-object-7.21.11.tgz#69d597086b6760c4126525cfa154f34631ff272c"
+  integrity sha512-0QZ8qP/3RLDVBwBFoWAwCtgcDZJVwA5LUJRZU8x2YFfKNuFq161wK3cuGrALu5yiPu+vzwTAg/sMWVNeWeNyaw==
+  dependencies:
+    "@babel/helper-annotate-as-pure" "^7.18.6"
+    "@babel/helper-create-class-features-plugin" "^7.21.0"
+    "@babel/helper-plugin-utils" "^7.20.2"
+    "@babel/plugin-syntax-private-property-in-object" "^7.14.5"
+
 "@babel/plugin-proposal-unicode-property-regex@^7.4.4":
   version "7.18.6"
   resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-unicode-property-regex/-/plugin-proposal-unicode-property-regex-7.18.6.tgz#af613d2cd5e643643b65cded64207b15c85cb78e"