feat: set and shopt directives (#929)

Co-authored-by: Andrey Nering <andrey@nering.com.br>

internal/slicesext/slicesext.go

@@ -0,0 +1,20 @@
+package slicesext
+
+import (
+	"golang.org/x/exp/constraints"
+	"golang.org/x/exp/slices"
+)
+
+func UniqueJoin[T constraints.Ordered](ss ...[]T) []T {
+	var length int
+	for _, s := range ss {
+		length += len(s)
+	}
+	r := make([]T, length)
+	var i int
+	for _, s := range ss {
+		i += copy(r[i:], s)
+	}
+	slices.Sort(r)
+	return slices.Compact(r)
+}