One of your dependencies, babel-preset-react-app, is importing the
“@babel/plugin-proposal-private-property-in-object” package without
declaring it in its dependencies. This is currently working because
“@babel/plugin-proposal-private-property-in-object” is already in your
node_modules folder for unrelated reasons, but it may break at any time.
babel-preset-react-app is part of the create-react-app project, which
is not maintianed anymore. It is thus unlikely that this bug will
ever be fixed. Add “@babel/plugin-proposal-private-property-in-object” to
your devDependencies to work around this error. This will make this message
go away.
解决方法
如果你使用npm，运行以下命令：
npm install --save-dev @babel/plugin-proposal-private-property-in-object
如果你使用yarn，运行以下命令：
yarn add --dev @babel/plugin-proposal-private-property-in-object
这些命令会将@babel/plugin-proposal-private-property-in-object包添加到你的devDependencies中，并解决报错。它会自动下载并安装该包的最新版本。