Galactic Unicorn: Add support for P4 and P8 pen modes.

libraries/galactic_unicorn/galactic_unicorn.cpp

@@ -576,6 +576,25 @@ namespace pimoroni {
           set_pixel(x, y, r, g, b);
         }
       }
+      else if(graphics->pen_type == PicoGraphics::PEN_P8 || graphics->pen_type == PicoGraphics::PEN_P4) {
+        int offset = 0;
+        graphics->frame_convert(PicoGraphics::PEN_RGB888, [this, offset](void *data, size_t length) mutable {
+          uint32_t *p = (uint32_t *)data;
+          for(auto i = 0u; i < length / 4; i++) {
+            int x = offset % 53;
+            int y = offset / 53;
+
+            uint32_t col = *p;
+            uint8_t r = (col & 0xff0000) >> 16;
+            uint8_t g = (col & 0x00ff00) >>  8;
+            uint8_t b = (col & 0x0000ff) >>  0;
+
+            set_pixel(x, y, r, g, b);
+            offset++;
+            p++;
+          }
+        });
+      }
     }
   }