Curses-menu

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* Use Poetry, some github actions changes. Not pushing this one to pypi.

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* Workaround vscode/windows-curses issue

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* Actually fixed bug that breaks doc build

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* Fixed bug that breaks doc build

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* Mostly just fixed bugs in tests
* Improved cross-platform functionality of CommandItem

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* Large rewrite and refactor of pretty much everything
* 100% test coverage
* Started using pre-commit for style
* Migrated from Travis to Github actions
* Type checking with mypy
* Better handling of exit item via item groups
* Some ability to test/debug the actual graphical output
* Fixed bugs