Update language on approach to transpiling node_modules

[outofambit]

In light of parcel-bundler/parcel#1655, I've updated this language to be more accurate to the current state of parcel.

[vercel]

This pull request is automatically deployed with Now.
To access deployments, click Details below or on the icon next to each push.

[DeMoorJasper]

This isn't 100% accurate but it is more accurate than the current state I guess. node_modules with a browserlist or engines that is more modern than the projects target will also be transpiled.

Unfortunately this isn't 100% reliable but is more an issue with how package.json is not standardised.

[mrcoles]

Are you saying the way it handles dependencies is to do default @babel/preset-env on node_modules/ files unless the package.json in that dependency has a "browserslist" or "engines.browsers" key specified in their package.json? I just spent an hour or two debugging why "browserslist": "Chrome >= 41" seemed to not be working the Swiper package.