internal/coding/charsets.go
func FindCharsetInHTML(html string) string {
	charsetMatches := metaTagCharsetRegexp.FindAllStringSubmatch(html, -1)
	if len(charsetMatches) > 0 {
		return charsetMatches[0][metaTagCharsetIndex]
	}
	return ""
}
func FindCharsetInHTML(html string) string {
	charsetMatches := metaTagCharsetRegexp.FindAllStringSubmatch(html, -1)
	if len(charsetMatches) > 0 {
		return charsetMatches[0][metaTagCharsetIndex]
	}
	return ""
}
// FindCharsetInHTML looks for charset in the HTML meta tag (v4.01 and v5).