Allow toggling fullscreen without restart and add keybind (#14714)

irr/include/IrrlichtDevice.h

@@ -179,6 +179,11 @@ public:
 	/** \return True if window is fullscreen. */
 	virtual bool isFullscreen() const = 0;
 
+	//! Enables or disables fullscreen mode.
+	/** Only works on SDL.
+	\return True on success. */
+	virtual bool setFullscreen(bool fullscreen) { return false; }
+
 	//! Checks if the window could possibly be visible.
 	/** If this returns false, you should not do any rendering. */
 	virtual bool isWindowVisible() const { return true; };