Additional custom fields

### Description of the problem

Some platforms allow quick actions to apply changes on issues/PRs through specific commands written on commit messages.

### Solution

Allow custom fields to be created with specific prompts or lists to fulfill some template.

For instance:

```
? Choose a gitmoji: ✨ - Introduce new features.
? Enter the commit title [24/48]: Add super awesome button
? Enter the commit message:
? Time spent on this issue: 32h
? The issue is complete already (y/N): y
```
_That is a heck of button_

If the last fields are filled, the final commit message would have `/spent 32h` and `/request_review` appended at the end, adding time-tracking features from GitLab.

This could be used not only for convenience, but also to help enforcing team patterns usage...

### Alternatives

Well, just type the full command on the message body... ~but that is not as cool~

### Additional context

I think this may be somewhat related to #780, but I chose to create a new one because this concept doesn't exist yet, unlike scopes which is already a feature.

### Validations

- [X] Follow our [Code of Conduct](https://github.com/carloscuesta/gitmoji-cli/blob/master/CODE_OF_CONDUCT.md)
- [X] Read the [Contributing Guide](https://github.com/carloscuesta/gitmoji-cli/blob/master/.github/CONTRIBUTING.md).
- [X] Check that there isn't already an issue requesting the same feature.