Document multiline input for devs and users

[yajo]

For devs, this feature, that was already working, is now documented.

For users, a default instruction text appears when using multiline mode.

Fix #54.

[kiancross]

Thanks for the PR. There's a few tests failing and also you need to run black . over the code, to ensure the formatting is correct.

[kiancross]

Thanks for fixing code style. Final thing is a couple of tests to make sure the following lines are covered:
https://coveralls.io/builds/33727110/source?filename=questionary%2Fprompts%2Ftext.py#L63

[yajo]

I had to fix one problem on your tests: you were using \n as the Enter key, while it is \r instead. Also another problem in my test. It should go ✔️ now.

[yajo]

So, could this be merged?

[kiancross]

@yajo Waiting to see what @tmbo thinks about leaving this as the same type vs creating a new one.

[yajo]

According to the new rules for Hacktoberfest 2020:

Pull requests labelled as hacktoberfest-accepted will count toward to Hacktoberest from any public repository on GitHub

So may I ask you please to label this PR as hacktoberfest-accepted? 🙏 🥺

[kiancross]

So may I ask you please to label this PR as hacktoberfest-accepted?

@tmbo Can you check this?

[tmbo]

already added it to the repository 👍