[doc] feat: Add VTool-R1 in the list of "awesome works using verl (volcengine#3036)

Add VTool-R1 into `Awesome work using verl`

### What does this PR do?

This PR adds a recent work built upon verl into the "Awesome work using
verl" Section of the README.md file.
Add VTool-R1: VLMs Learn to Think with Images via Reinforcement Learning
on Multimodal Tool Use, into `Awesome work using verl`

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Author: JingchengYang4

README.md

@@ -230,6 +230,7 @@ verl is inspired by the design of Nemo-Aligner, Deepspeed-chat and OpenRLHF. The
 - [PF-PPO](https://arxiv.org/abs/2409.06957): Policy Filtration for PPO based on the reliability of reward signals for more efficient and robust RLHF.
 - [RACRO](https://github.com/gyhdog99/RACRO2): Build multi-modal reasoning models via decoupling it into query-conditioned captioning and text-only reasoning ![GitHub Repo stars](https://img.shields.io/github/stars/gyhdog99/RACRO2)
 - [Agent Lightning](https://github.com/microsoft/agent-lightning): A flexible and extensible framework that enables seamless agent optimization for any existing agent framework. ![GitHub Repo stars](https://img.shields.io/github/stars/microsoft/agent-lightning)
+- [VTool-R1](https://github.com/VTOOL-R1/vtool-r1): VLMs Learn to Think with Images via Reinforcement Learning on Multimodal Tool Use. ![GitHub Repo stars](https://img.shields.io/github/stars/VTOOL-R1/vtool-r1)
 
 and many more awesome work listed in [recipe](recipe/README.md).