create scaffold for loading screen

internal/page/DownloadingAssets.go

@@ -0,0 +1,28 @@
+package page
+
+import (
+	"github.com/veandco/go-sdl2/sdl"
+)
+
+type DownloadingAssets struct {
+}
+
+func (p *DownloadingAssets) Init(ctx *PageCtx) error {
+	return nil
+}
+
+func (p *DownloadingAssets) HandleEvent(event *sdl.Event) error {
+	return nil
+}
+
+func (p *DownloadingAssets) Update(dt float32) error {
+	return nil
+}
+
+func (p *DownloadingAssets) Render() error {
+	return nil
+}
+
+func (p *DownloadingAssets) Destroy() error {
+	return nil
+}