docs: update readme

CONTRIBUTING.md

@@ -0,0 +1,12 @@
+# Contributing to ReadFrog
+
+Thank you for your interest in contributing!
+
+By submitting a pull request or any contribution to this repository, you agree that your contribution will be licensed under:
+
+- GNU GPLv3, and
+- A separate commercial license granted by FEELIO TECHNOLOGIES LTD.
+
+You represent that you have the right to submit the contribution and that it does not infringe any third-party rights.
+
+If you do not agree to these terms, please do not submit contributions.

README.md

@@ -49,6 +49,7 @@ Master languages effortlessly and deeply with AI, right in your browser.
   - [📖 Read Article](#-read-article)
 - [🤝 Contribute](#-contribute)
   - [Contribute Code](#contribute-code)
+- [📜 Commercial License Grant](#-commercial-license-grant)
 - [❤️ Sponsors](#️-sponsors)
 
 <br/>
@@ -255,6 +256,10 @@ Ask AI to understand the project: [Dosu](https://app.dosu.dev/29569286-71ba-47dd
 
 Check out the [Contribution Guide](https://readfrog.app/en/tutorial/code-contribution/contribution-guide) for more details.
 
+ReadFrog is dual-licensed under GPLv3 and a commercial license.
+
+See [CONTRIBUTING.md](./CONTRIBUTING.md) for contributor licensing terms.
+
 <a href="https://github.com/mengxi-ream/read-frog/graphs/contributors">
   <table>
     <tr>
@@ -287,6 +292,16 @@ Check out the [Contribution Guide](https://readfrog.app/en/tutorial/code-contrib
 
 </div>
 
+## 📜 Commercial License Grant
+
+<img src="assets/tabbit.avif" alt="Tabbit" height="20" /> **Meituan Tabbit Browser Team**: Free license (at no cost) for closed-source commercial use, limited to v1.21.3 and earlier versions (commit [`724863f`](https://github.com/mengxi-ream/read-frog/commit/724863fdbc2d777766cada6c111235534ee03ca0)). Granted on March 3, 2025, 9:00 AM (Vancouver Time, UTC-8).
+
+<div align="right">
+
+[![][back-to-top]](#readme-top)
+
+</div>
+
 ## ❤️ Sponsors
 
 Every donation helps us build a better language learning experience. Thank you for supporting our mission!

README.zh-CN.md

@@ -49,6 +49,7 @@
   - [📖 阅读文章](#-阅读文章)
 - [🤝 贡献](#-贡献)
   - [贡献代码](#贡献代码)
+- [📜 商业授权](#-商业授权)
 - [❤️ 赞助者](#️-赞助者)
 
 <br/>
@@ -253,6 +254,10 @@ Read Frog 的愿景是为各个级别的语言学习者提供易于使用、智
 
 查看[贡献指南](https://readfrog.app/zh/tutorial/code-contribution/contribution-guide)了解更多详情。
 
+ReadFrog 采用 GPLv3 和商业许可双重授权。
+
+贡献者许可条款请参阅 [CONTRIBUTING.md](./CONTRIBUTING.md)。
+
 <a href="https://github.com/mengxi-ream/read-frog/graphs/contributors">
   <table>
     <tr>
@@ -285,6 +290,16 @@ Read Frog 的愿景是为各个级别的语言学习者提供易于使用、智
 
 </div>
 
+## 📜 商业授权
+
+<img src="/assets/tabbit.avif" alt="Tabbit" height="20" /> **美团 Tabbit 浏览器团队**：**免费**授权闭源商业使用，授权范围限于 v1.21.3 及之前的版本（commit [`724863f`](https://github.com/mengxi-ream/read-frog/commit/724863fdbc2d777766cada6c111235534ee03ca0)）。授权日期：2025 年 3 月 3 日上午 9:00（温哥华时间，UTC-8）。
+
+<div align="right">
+
+[![][back-to-top]](#readme-top)
+
+</div>
+
 ## ❤️ 赞助者
 
 每一笔捐赠都帮助我们构建更好的语言学习体验。感谢您支持我们的使命！