[docs] Fix minor typos and a doc link (#33)

Author: xinhuagu

CONTRIBUTING.md

@@ -43,7 +43,7 @@ Of course, if you have a good idea, you can also propose it directly on GitHub D
     ```shell
     git checkout -b a-feature-branch #Recommended  
     ```
-5. Submit the coed as a commit, the commit message format specification required: [module name or type name]feature or bugfix or doc: custom message.  
+5. Submit the code as a commit, the commit message format specification required: [module name or type name]feature or bugfix or doc: custom message.  
     ```shell
     git add <modified file/path> 
     git commit -m '[docs]feature: necessary instructions' #Recommended 
@@ -78,9 +78,9 @@ git push origin --delete a-dev-branch
 On the master/main branch, you can do the following to sync the upstream repository:
 
 ```shell
-git remote add upstream https://github.com/a2ap/a2a4j.git #Bind the remote warehouse, if it has been executed, it does not need to be executed again
-git checkout master 
-git pull upstream master
+git remote add upstream https://github.com/a2ap/a2a4j.git #Bind the remote repository, if it has been executed, it does not need to be executed again
+git checkout main 
+git pull upstream main
 ```
 
 <br>

CONTRIBUTING_CN.md

@@ -21,7 +21,7 @@
 ### 查找任务
 
 找到您感兴趣的问题！在我们的 GitHub 仓库问题列表中，我们通常会发布一些带有标签 `good first issue` 或 `status: volunteer wanted` 的问题。  
-这些问题欢迎贡献者领取并为止贡献。其中，`good first issues` 通常门槛较低，适合新人。
+这些问题欢迎贡献者领取并为之贡献。其中，`good first issues` 通常门槛较低，适合新人。
 
 当然，如果您有好的想法，也可以直接在 GitHub Discussion 中提议或与社区联系。
 
@@ -73,8 +73,8 @@ git push origin --delete a-dev-branch
 
 ```shell
 git remote add upstream https://github.com/a2ap/a2a4j.git #绑定远程仓库，如果已经执行过，则不需要再次执行
-git checkout master 
-git pull upstream master
+git checkout main 
+git pull upstream main
 ```
 
 <br>

README_CN.md

@@ -263,7 +263,7 @@ curl -X POST http://localhost:8089/a2a/server \
 
 ## 🤝 贡献
 
-我们欢迎贡献！请查看我们的[贡献指南](CONTRIBUTING.md)了解详情。
+我们欢迎贡献！请查看我们的[贡献指南](CONTRIBUTING_CN.md)了解详情。
 
 1. Fork 仓库
 2. 创建功能分支: `git checkout -b feature/my-feature`