- add NcMenuSection::new_separator() constructor.
- rename constructor method for an empty NcInput to new();
- fix notcurses_getc_blocking() function name and error logic.
- improve comments.
- change type of NCMENU_OPTION_* to u64 (like in C API)
- fix error_str![] macro.
- improve error messages.
- new example poc-menu (WIP).
- improve constructors for NcMenu*.
- divide NcMenu* methods into submodules.
- fix return type for NcPlane constructors.
- use NcResult on functions returning references.
- fix a couple of Notcurses methods.
- add more NcChannelPair methods.
- refactor NcInput constructors.
- rename error_ptr![] to error_ref_mut![]
- new macro cstring_mut![].
- new error_ref![] macro.
- update examples & tests.
- bump version in readme.
