Add a function to continuously get keystrokes until the "application is quited" or "keyboard.Close() called".

[SakthiMahendran]

Generally most of the application wants to get continues keystrokes.

For example imagine a game played through keyboard we have to listen for keystrokes until the game ends and also I am using this library to create a typewriting application which have to listen for keys until the application is quite.

Currently this library only supports getting single keystroke and n number of keystrokes. So I am recommending to add a function that gives this feature.

If there is a function for getting single keystroke (GetSingleKey()) then why not for getting continuous keystroke.

Hope you understand 😊.