Display initial graphical/text mode info

Previously, this.graphical_mode and the "screen-set-mode" message was
set/sent when the miscellaneous output register was modified. Now that
the method of determining the video mode has changed, screen-set-mode
didn't get sent for the default mode.

src/vga.js

@@ -178,6 +178,7 @@ function VGAScreen(cpu, bus, vga_memory_size)
 
     /** @type {boolean} */
     this.graphical_mode = false;
+    setTimeout(() => { bus.send("screen-set-mode", this.graphical_mode); }, 0);
 
     /*
      * VGA palette containing 256 colors for video mode 13, svga 8bpp, etc.