fix: add ioeither

Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>

bytes/monoid_test.go

@@ -0,0 +1,11 @@
+package bytes
+
+import (
+	"testing"
+
+	M "github.com/ibm/fp-go/monoid/testing"
+)
+
+func TestMonoid(t *testing.T) {
+	M.AssertLaws(t, Monoid)([][]byte{[]byte(""), []byte("a"), []byte("some value")})
+}