Add paper and codebase

[ChengpengLi1003]

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Paper: Long CoT with tool(code Interpreter):

1. START: Self-taught Reasoner with Tools (https://arxiv.org/abs/2503.04625)
2. CoRT: Code-integrated Reasoning within Thinking (https://arxiv.org/abs/2506.09820)

Code Base: RL framework for longCoT with tool

CoRT: https://github.com/ChengpengLi1003/CoRT