The cursor keys in application mode are not match the constants

[chen3feng]

https://tldp.org/HOWTO/Keyboard-and-Console-HOWTO-21.html
When the terminal is in application cursor key mode, the cursor keys produce Esc O x and otherwise Esc [ x where x is one of A, B, C, 'D`. Certain programs put the terminal in application cursor key mode; if you kill them with kill -9, or if they crash, then the mode will not be reset.

The cursor keys are different between the two modes:
https://learn.microsoft.com/en-us/windows/console/console-virtual-terminal-sequences#cursor-keys

The key code constants only match the normal mode.

To fix this, I think the easiest way is to reset the cursor key mode to normal:

def readkey() -> str:
    """Get a keypress. If an escaped key is pressed, the full sequence is
    read and returned as noted in `_posix_key.py`."""

    # Reset the terminal to normal cursor key mode
    # https://tldp.org/HOWTO/Keyboard-and-Console-HOWTO-21.html
    print("\x1b[?1l", end='')

    # It can be quite long when input is from IME.
    return _readkeybuffer(1000)

If you agree with me, I can create a PR or you can also use the above code directly.

[Cube707]

I don't think pushing that onto every call to readkey() for every user is a good idea. When needed it can be added by applications on startup once, which is the much better solution.

There are development efforts to create a context-manager for this lib which would be a good place to add this code, but that is far of from beeing ready to be shipped and I don't have much time to work on it currently.

[Cube707]

this is somewhat related to #24