message: Fix typo in MockFunctions.md
  Impementation -> Implementation
diff: @@ -167,7 +167,7 @@ test('should fetch users', () => {
  axios.get.mockResolvedValue(resp);
  // or you could use the follwing depending on your use case:
  - // axios.get.mockImpementation(() => Promise.resolve(resp))
  + // axios.get.mockImplementation(() => Promise.resolve(resp))
  return Users.all().then(users => expect(users).toEqual(resp.data));
  });
  