Add a licnese

[wedu-nvidia]

Hi authors

I’m currently a research scientist at NVIDIA working on mathematical reasoning. I came across your repository, and I really appreciate the work you’ve done!

We’re also working on mathematical reasoning and would love to use some of your code for answer/problem extraction in our research. However, I noticed that the repository doesn’t have a license, which means we’re not sure how we can use or reference your work.

[Haoxiang-Wang]

Hi @huybery @hzhwcmhf @yangapku @ToheartZhang ,
Could you add a license to this repo?