Move app packages under internal

internal/assets/assets.go

@@ -0,0 +1,23 @@
+package assets
+
+import (
+	"bytes"
+	"embed"
+	"image"
+	"image/png"
+)
+
+//go:embed *.png *.svg
+var files embed.FS
+
+func MustPNG(name string) image.Image {
+	data, err := files.ReadFile(name)
+	if err != nil {
+		panic(err)
+	}
+	img, err := png.Decode(bytes.NewReader(data))
+	if err != nil {
+		panic(err)
+	}
+	return img
+}