Add DeepSeek template and template register

[wheresmyhair]

Add DeepSeek template and template register
Also solves the template init error when using python >= 3.11 (due to @DataClass decorator)

[research4pan]

LGTM. The register operation can be made simpler for easier understanding and maintenance.

src/lmflow/models/hf_decoder_model.py

• [Style] line 463: recommend to put line 470 in front of line 463. Unlikely events come later, which is better for understanding, and sometimes performance.

src/lmflow/utils/conversation_template.py

• [Style, Architecture] line 13, 295-317: the registration function can be put in a different file, such as utils/template/custom.py or utils/template/base.py.
  • For standard templates, we can define different templates first, then directly map names to templates in line 13. This way the code is cleaner and easier to extend. In current styles, if we would like to add more arguments to templates, register_template has to adapt accordingly, which will be a problem in maintenance.
  • For customized templates, we can use this register function, with some examples provided in README.