func EqualFold(s, t []rune) bool {
	for len(s) > 0 && len(t) > 0 {
		var sr, tr rune
		sr, s = s[0], s[1:]
		tr, t = t[0], t[1:]
		if tr == sr {
			continue
		}
		if tr < sr {
			tr, sr = sr, tr
		}
		if tr < utf8.RuneSelf {
			if 'A' <= sr && sr <= 'Z' && tr == sr+'a'-'A' {
				continue
			}
			return false
		}
		r := unicode.SimpleFold(sr)
		for r != sr && r < tr {
			r = unicode.SimpleFold(r)
		}
		if r == tr {
			continue
		}
		return false
	}
	return len(s) == len(t)
}
EqualFold reports whether s and t are equal under Unicode case-folding.
copied from strings.EqualFold
package runes
import (
	"unicode"
	"unicode/utf8"
)