Sys.getChar

I have been using [IHx](github.com/ianxm/ihx)'s `ConsoleReader` class to make REPLs within Haxe that can save their command history and navigate between it. I expected this to work when compiling for NodeJS, but got the exception that Sys.getChar() isn't implemented in hxnodejs. Could it be?

I see [here](https://github.com/HaxeFoundation/hxnodejs/blame/2058979cdade340749aa145734fb09b4b888b567/src/Sys.hx#L93) that it was stubbed this way three years ago and hasn't been touched since. If the implementation is easy enough, I could do it and PR.