Add Indonesia Language (#64)

* Add Indonesia Language
* Add "idn", "ind" for Indonesia Language
* Add test for Indonesia language

Co-authored-by: rizkyadhi <me@rizkyadhi.com>
Co-authored-by: Dobrosław Żybort <matrixik@gmail.com>

languages_substitution.go

@@ -17,6 +17,7 @@ func init() {
 		&fiSub,
 		&frSub,
 		&grSub,
+		&idSub,
 		&kkSub,
 		&nbSub,
 		&nlSub,
@@ -95,6 +96,10 @@ var grSub = map[rune]string{
 	'ϋ': "u",
 }
 
+var idSub = map[rune]string{
+	'&': "dan",
+}
+
 var kkSub = map[rune]string{
 	'&': "jane",
 	'ә': "a",

slug.go

@@ -71,6 +71,8 @@ func MakeLang(s string, lang string) (slug string) {
 		slug = SubstituteRune(slug, frSub)
 	case "gr", "el", "ell":
 		slug = SubstituteRune(slug, grSub)
+	case "id", "idn", "ind":
+		slug = SubstituteRune(slug, idSub)
 	case "kz", "kk", "kaz":
 		slug = SubstituteRune(slug, kkSub)
 	case "nb", "nob":

slug_test.go

@@ -107,6 +107,7 @@ func TestSlugMakeLang(t *testing.T) {
 		{"fr", "This & that", "this-et-that", true},
 		{"fr", "This @ that", "this-arobase-that", true},
 		{"gr", "This & that", "this-kai-that", true},
+		{"id", "This & that", "this-dan-that", true},
 		{"ell", "This & that", "this-kai-that", true},
 		{"Ell", "This & that", "this-kai-that", true},
 		{"kk", "This & that", "this-jane-that", true},