Add feature to mocha

Any chance that you'll take the randomization feature from rocha and apply it to mocha directly?

There's already an open issue but still no PR. https://github.com/mochajs/mocha/issues/902

Start by reading how rocha currently randomizes Mocha test order, then review the linked Mocha issue #902 for the upstream context. Confirm the expected randomization behavior and identify the Mocha entry points and tests involved; done means Mocha provides the equivalent feature directly.

Written by the indexing model from the issue text.