Add a print question type

[RhetTbull]

What is the problem that this PR addresses?
Adds print type to dictionary style prompts. Closes #207.

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How did you solve it?
Modified prompt() to handle a print type that prints a message (with/without optional style). The name field is optional when using print. print does not return a value and does not add an entry to the returned dict from prompt(); it only outputs text. print does work with the when keyword so the message can be conditionally printed.

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Checklist

• I have read the Contributor's Guide.
• I will check that all automated PR checks pass before the PR gets reviewed.

Note: several tests in tests/prompts/test_select.py failed with "too many open files". However, these same tests failed before the PR changes. I'm using a Mac running Catalina 10.15.7. All other tests (including the tests added for this PR) passed.

tests/prompts/test_select.py::test_jk_and_shortcut_conflict_avoided_by_disabling_ij_keys FAILED                                                 [ 94%]
tests/prompts/test_select.py::test_select_shortcuts FAILED                                                                                      [ 95%]
tests/prompts/test_select.py::test_select_no_arrow_keys FAILED                                                                                  [ 95%]
tests/prompts/test_select.py::test_select_no_shortcuts FAILED                                                                                   [ 96%]
tests/prompts/test_select.py::test_select_default_has_arrow_keys FAILED

mypy checks passed:

mypy questionary
Success: no issues found in 17 source files

The pycodestyle test required by contributor's guide had many failures (mostly long lines) that were already present in the source code -- not changed in this PR. I fixed the changes in the PR to ensure they introduced no new pycodestyle errors. I did add # noqa to two lines in prompt.py that were 80 and 85 lines long respectively because changing the code would have been much less clean (would require an if/then block instead of an inline which was easier to read).

Note: running black on the tests/ directory would have changed a bunch of the existing import statements so I made sure my new tests were blackified but did not run black on the existing code.

[kiancross]

Thanks for this PR.

The pycodestyle test required by contributor's guide had many failures (mostly long lines) that were already present in the source code -- not changed in this PR.

This part of the contributor's guide has been updated (if you look at the latest version rather than stable, you will see this).

You should just be able to run make develop and then make lint to apply all formatting rules. The # noqa comments should not be necessary, as the aforementioned commands will sort out all line length issues.

[kiancross]

This all looks great - thanks. I've left a comment below.

[kiancross]

Looks good to me - thanks for the PR!