Get the initial copyright notice displaying

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

internal/assetstore/assetstore.go

@@ -8,6 +8,8 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/hajimehoshi/ebiten"
+
 	"code.ur.gs/lupine/ordoor/internal/config"
 	"code.ur.gs/lupine/ordoor/internal/data"
 	"code.ur.gs/lupine/ordoor/internal/idx"
@@ -44,6 +46,7 @@ type AssetStore struct {
 	fonts     map[string]*Font
 	generic   *data.Generic
 	idx       *idx.Idx
+	images    map[string]*ebiten.Image
 	maps      map[string]*Map
 	menus     map[string]*Menu
 	objs      map[string]*Object
@@ -109,6 +112,7 @@ func (a *AssetStore) Refresh() error {
 	a.entries = newEntryMap
 	a.fonts = make(map[string]*Font)
 	a.idx = nil
+	a.images = make(map[string]*ebiten.Image)
 	a.maps = make(map[string]*Map)
 	a.menus = make(map[string]*Menu)
 	a.objs = make(map[string]*Object)