* Update README.md

Polish README
Co-authored-by: NZeyu Chen <chenzeyu01@baidu.com>
Co-authored-by: NSteffy-zxf <48793257+Steffy-zxf@users.noreply.github.com>

* optimize demo and cv reader

* finish coding predict

* optimize predict pr

* optimize _postprocessing

* optim namedtuple

* Modify the coding format of senta_demo.py and lac_demo.py

* Add the toxic dataset and multi-label task

* Add the multi_label classification demo

* Update teh demo text-cls and seq-label

* Fix the encoding format