Default targets for preset-env shall be “defaults”

No `.browserslist` file implies a `.browserslist` file with content `default`, and this means support for IE 11 and this means, as of https://kangax.github.io/compat-table/es6/, only some ES2015/ES6.

https://babeljs.io/docs/en/babel-preset-env#targets says “Sidenote, if no targets are specified, @babel/preset-env will transform all ECMAScript 2015+ code by default.”

Apart from the fact that there is a “caveat” dead-link-hint above this citation, assuming the wording means ”will transform TO ES2015+ by default" (thus it will run on any ES2015 javascript engine), please change the default of no "targets", do mean `targets: "defaults"`.