Add -after to insert html after the generated content

go/blog/blog.go

	noDefaultStyle    bool
	printDefaultStyle bool
	title             string
	after             string
}
var dataPath string = "blog.yaml"
	flag.BoolVar(&flags.noDefaultStyle, "no-default-style", false, "Don't use the default styles")
	flag.BoolVar(&flags.printDefaultStyle, "print-default-style", false, "Print the default styles")
	flag.StringVar(&flags.title, "title", "A blog", "Custom `title` to use")
	flag.StringVar(&flags.after, "after", "", "Insert additional `html` at the end of the generated page")
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage: %s [flags] [<blog.yaml> [<blog.html>]]\n\n", os.Args[0])
		document.title = baseTitle;
	}
	</script>`)
	if flags.after != "" {
		fmt.Fprintf(out, "\n%s\n", flags.after)
	}
	fmt.Fprintf(out, "\n</body>\n</html>\n")
	out.Close()