docs: update README.md

Author: nsonanh

README.md

@@ -39,4 +39,7 @@ println!("result: {}", result_str); // should prints "Hello, World!"
 Charset used :
 ```
 àáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿĀāĂ㥹ĆćĈĉĊċČčĎďĐđĒēĔĕĖėĘęĚěĜĝĞğĠġĢģĤĥĦħĨĩĪīĬĭĮįİıIJijĴĵĶķĸĹĺĻļĽľĿŀŁłŃńŅņŇňʼnŊŋŌōŎŏŐőŒœŔŕŖŗŘřŚśŜŝŞşŠšŢţŤťŦŧŨũŪūŬŭŮůŰűŲųŴŵŶŷŸŹźŻżŽžſƀƁƂƃƄƅƆƇƈƉ=_-`~|[]{}ƞ?,()^*$%!#.ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/
-```
+```
+
+## License
+[MIT](LICENSE-MIT) or [Apache License 2.0](LICENSE-APACHE) (at your option).