Qs-codec

* [CHORE] drop support for Python 3.8 and update dependencies for Python 3.9+

* [FIX] fix `EncodeUtils.encode` for non-BMP characters
* [CHORE] refactor `EncodeUtils` and `DecodeUtils`
* [CHORE] add more tests

* [FIX] fix encoding non-BMP characters when using `charset=Charset.LATIN1`

* [FEAT] add `DecodeOptions.raise_on_limit_exceeded` option ([11](https://github.com/techouse/qs_codec/pull/11))
* [CHORE] remove dead code in `Utils`
* [CHORE] add more tests
* [CHORE] update dependencies

* [FIX] `decode`: avoid a crash with `comma=True`, `charset=Charset.LATIN1`, `interpret_numeric_entities=True`
* [CHORE] add more tests

* [FEAT] add `DecodeOptions.strict_depth` option to throw when input is beyond depth ([8](https://github.com/techouse/qs_codec/pull/8))