src/vs/platform/keybinding/common/abstractKeybindingService.ts/AbstractKeybindingService/mightProducePrintableCharacter
class AbstractKeybindingService:	mightProducePrintableCharacter(event: IKeyboardEvent): boolean {
		if (event.ctrlKey || event.metaKey) {
			// ignore ctrl/cmd-combination but not shift/alt-combinatios
			return false;
		}
		// weak check for certain ranges. this is properly implemented in a subclass
		// with access to the KeyboardMapperFactory.
		if ((event.keyCode >= KeyCode.KeyA && event.keyCode <= KeyCode.KeyZ)
			|| (event.keyCode >= KeyCode.Digit0 && event.keyCode <= KeyCode.Digit9)) {
			return true;
		}
		return false;
	}