Add hints support for checkboxes

[rizkyarlin]

This PR addresses #340 in this repo.

I also would like to use this feature for mac-cleanup/mac-cleanup-py#80

If this looks okay, I'll create the tests. Thank you for the awesome package!

[Cube707]

Sorry I don't have much time to test this right now, but my first question is: what if a user only wants hints for some of the questions? And what if the list-length doesn't match the number of questions? Should it raise an error or just guess?

Maybe a dict would be a better choice to clearly map hints to a specific choice? Or does this lead to other problem?

Not really stuff you need to answer, just what pops into my head when looking at the changes

[rizkyarlin]

I agree that dict would be better. I just followed the example from #340 . I'll update my PR later

[rizkyarlin]

I updated my PR:

1. use dict for hints
2. add hints to List Question type
3. add integration tests
4. Add color for hints.
5. Update docs/usage.md (I'm not sure about the format of the docs)

Please take a look @Cube707

[efa2d19]

@Cube707 any updates on when you can check it out?
This will really help us close up the issue

[Cube707]

sorry it took so long, but I now had the time to fix it all up