docs: standardize server configuration naming in documentation (#56)

- Rename the example "github" server configuration to "gitea-mcp" in all README files

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/56
Co-authored-by: appleboy <appleboy.tw@gmail.com>
Co-committed-by: appleboy <appleboy.tw@gmail.com>

README.zh-cn.md

@@ -54,7 +54,7 @@ Model Context Protocol (MCP) 是一种协议，允许通过聊天界面整合各
       }
     ],
     "servers": {
-      "github": {
+      "gitea-mcp": {
         "command": "docker",
         "args": [
           "run",