make fn optional in app.Run

examples/minimal/main.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	_ "embed"
+
+	t "git.iwakura.rip/grng/tiramisu"
+	webview "github.com/webview/webview_go"
+)
+
+//go:embed index.html
+var html string
+
+func main() {
+	app := t.New(t.TiramisuOptions{
+		Debug:  true,
+		Width:  800,
+		Height: 600,
+		Title:  "Tiramisu",
+		Hints:  webview.HintFixed,
+	})
+
+	app.HTML(html)
+	app.Run()
+}