Enhance keyboard support

Given that you already have good support for keyboard as a gaming input device, it would be nice to have GameInput version of actual input for entered symbols.
By that I mean your current implementation basically mimics or replaces WM_ events from WINAPI, however if game engine also would want to support some type of chatting or entering, let's say names for profile, etc, you would still be bound to use WM_CHAR (which often then not is pain in the back to debug if it fails on XBox devkit) events for entering something.
And anyone who tried to use it, knows that it's a prettiest solution to sync with other input systems.

I think if the goal is to gradually replace all the input code for engines/apps in the future, then it's a next big step in "keyboard department" for this library.

P.S. Can't set label myself, but I think it should be feature request.

Review the existing keyboard support and how it currently mirrors WINAPI WM_ events, then define how entered symbols should be exposed through GameInput. Done means game engines can support text entry, such as chat or profile names, without depending on WM_CHAR events.