Revert "Removes Webpack/Babel in favor of SWC"

[ralexmatthews]

Hey, I actually found an issue with this. In vanilla node.js apps without a build process, you would need to import it with

const EasyPostClient = require("@easypost/api").default;

I am gonna continue to look to switching, but for now that would be a breaking change, so I am reverting it