Hi there. I've been using fancy-test (by way of @oclif/test) and using Jest as my test runner (since that's what I was already using to run all the tests in my monorepo), and it pretty much just works. It's been great.

The only thing I've run into is that I have to include @types/jest in my monorepo, and since I do, when I try to build my package with TypeScript, I get some errors that look like this:

../../node_modules/@types/jest/index.d.ts:44:13 - error TS2403: Subsequent variable declarations must have the same type.  Variable 'test' must be of type 'TestFunction', but here has type 'It'.

44 declare var test: jest.It;
               ~~~~

  ../../node_modules/@types/mocha/index.d.ts:2817:13
    2817 declare var test: Mocha.TestFunction;
                     ~~~~
    'test' was also declared here.

I've been able to get around this by setting "skipLibCheck": true in my tsconfig.json, but I'd like to not skip checks if possible.

This PR brings in mocha's Done type (basically the same kind of thing that was already done in d011192). It also moves @types/mocha to devDependencies instead of dependencies, since after this change as far as I can tell the mocha types aren't used in the src code itself. By moving @types/mocha to devDependencies, if you add fancy-test it to a project, it won't add @types/mocha, too, and you can avoid clashes with @types/jest.