Unclear documentation for babelrc option

[The docs for babelrc option](https://babeljs.io/docs/en/options#babelrc) do not clearly specify what happens when `babelrc: false`. Does it stop searching up the directory tree and look just for a single file or does it stop using babelrc files altogether?

It's not behaving the way I'd expect and I'm not sure if that's because it's broken as [many people have reported](https://github.com/babel/babel-loader/issues/464#issuecomment-411390976) or if it's because I'm making some wrong assumptions about how it should work

Start with the linked Babel options documentation at the babelrc section and verify what babelrc: false does, including whether it stops directory searching or disables babelrc files. Update that documentation to state the behavior clearly and explain the relevant assumption; done when the option's effect is unambiguous to readers.

Written by the indexing model from the issue text.