Wrap class field initializers with IIFE to workaround https://webkit.org/b/236843
See our website @babel/plugin-bugfix-safari-class-field-initializer-scope for more information.
Using npm:
npm install --save-dev @babel/plugin-bugfix-safari-class-field-initializer-scope
or using yarn:
yarn add @babel/plugin-bugfix-safari-class-field-initializer-scope --dev