📝 Docs: Document that mocha will search for mocha configs by going through parent directories

[JavaScriptBach]

Mocha currently searches through parent directories to find a mocharc config:

mocha/lib/cli/options.js

Line 182 in 37deed2

const filepath = args.package || findUp.sync(mocharc.package);

But this behavior isn't documented in https://mochajs.org/#configuring-mocha-nodejs, which only says to create the mocharc in your package's root directory.

[Bernice55231]

Hi, I am interested in polishing the documents, can I take this issue?