a lot of improvements in language codes

language_codes/src/commonTest/kotlin/UnknownIetfLanguageTests.kt

@@ -0,0 +1,16 @@
+package dev.inmo.micro_utils.language_codes
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class UnknownIetfLanguageTests {
+    @Test
+    fun commonTestOfParentCode() {
+        knownLanguageCodes.forEach {
+            val language = IetfLang.UnknownIetfLang(it.code)
+            assertEquals(it.code, language.code)
+            assertEquals(it.withoutDialect, language.withoutDialect)
+            assertEquals(it.parentLang ?.code, language.parentLang ?.code)
+        }
+    }
+}