LibUnicode: Add Punycode::encode

Author: https://github.com/skyrising
Commit: cfd0a60863
Pull-request: https://github.com/SerenityOS/serenity/pull/19414
Reviewed-by: https://github.com/AtkinsSJ
Reviewed-by: https://github.com/nico
Reviewed-by: https://github.com/shannonbooth
Reviewed-by: https://github.com/trflynn89

Tests/LibUnicode/TestPunycode.cpp

@@ -47,4 +47,11 @@ TEST_CASE(decode)
     EXPECT(decode("Nåväl hej vänner"sv).is_error());
 }
 
+TEST_CASE(encode)
+{
+#define CASE(a, b) EXPECT_EQ(TRY_OR_FAIL(encode(a)), b);
+    ENUMERATE_TEST_CASES
+#undef CASE
+}
+
 }