[Feature Request] Check that I meant to submit a test file.

I sometimes accidently submit the test file rather than the code file. This is because I'm running this a lot

```bash
ruby something_test.rb
```

and then sometimes my fingers just automatically type the same filename for `exercism submit`.

It would be nice that i I submit one file and it matches the test pattern, the CLI asks whether I meant to submit just the test file before creating the iteration.