Get the initial copyright notice displaying

This is really awful, but it's nice to check it off.

internal/assetstore/image.go

@@ -0,0 +1,42 @@
+package assetstore
+
+import (
+	"image"
+	"os"
+
+	"github.com/hajimehoshi/ebiten"
+	_ "github.com/samuel/go-pcx/pcx" // PCX support
+)
+
+func (a *AssetStore) Image(name string) (*ebiten.Image, error) {
+	name = canonical(name)
+	if img, ok := a.images[name]; ok {
+		return img, nil
+	}
+
+	// baps, ordoor, geas store .pcx files in Pic
+	// TODO: SL stores .bmp files in Res
+	filename, err := a.lookup(name, "pcx", "Pic")
+	if err != nil {
+		return nil, err
+	}
+
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	rawImg, _, err := image.Decode(f)
+	if err != nil {
+		return nil, err
+	}
+
+	img, err := ebiten.NewImageFromImage(rawImg, ebiten.FilterDefault)
+	if err != nil {
+		return nil, err
+	}
+
+	a.images[name] = img
+	return img, nil
+}