Consider switching to babel.config.json

[kmonahan]

Currently, Gesso includes a .babelrc file for Babel configuration. As of Babel 7, project-level configuration should be in babel.config.json instead, as .babelrc won't be applied to node_modules. (See https://babeljs.io/docs/en/configuration and babel/babel-loader#171 (comment) for reference.) Most of the time, this doesn't make any difference, since node_modules are excluded from the babel_loader in the webpack config anyway. However, some modules (e.g. https://swiperjs.com/get-started/) can be imported as ES6 modules and require transpiling for IE11. Switching to babel.config.json would allow a dev to whitelist modules as needed in the webpack config.