Add diagram for CI/CD workflow

.github/workflows/README.md

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+## 流程图（英文）
+
+```mermaid
+graph LR
+    A[Start GitHub Actions] -->|Trigger on PR or push to main, or manual dispatch| B(Set Up Environment)
+    B --> C(Build Test App)
+
+    subgraph C[Build Test App]
+        C1([Checkout Code]) --> C2([Install Python Dependencies])
+        C2 --> C3([Build Application with ESP-IDF])
+        C3 --> C4([Upload Binaries to Artifacts])
+    end
+
+    C --> D[Simulate Test on WokWi]
+
+    subgraph D[Simulate Test on WokWi]
+        D1([Checkout Repository]) --> D2([Set up Python])
+        D2 --> D3([Download Built Binaries])
+        D3 --> D4([Install Python Packages for PyTest])
+        D4 --> D5([Run PyTest in WokWi Simulator])
+        D5 --> D6([Upload PyTest Results])
+    end
+
+    D --> E[Publish Test App Results]
+
+    subgraph E[Publish Test App Results]
+        E1([Download Test Results]) --> E2([Publish Test Results])
+    end
+
+    classDef startNode fill:#f9f,stroke:#333,stroke-width:4px;
+    class A startNode;
+    classDef subgraphBox fill:#bbf,stroke:#f66,stroke-width:2px,padding:10px;
+    class C,D,E subgraphBox;
+```
+
+## 流程图（中文）
+
+```mermaid
+graph LR
+    A[启动 GitHub Actions] -->|触发主分支的拉取请求、推送或手动触发| B(设置环境)
+    B --> C(构建测试应用)
+
+    subgraph C[构建测试应用]
+        C1([检出代码]) --> C2([安装Python依赖])
+        C2 --> C3([使用ESP-IDF构建应用])
+        C3 --> C4([上传二进制文件到工件])
+    end
+
+    C --> D[在WokWi上模拟测试]
+
+    subgraph D[在WokWi上模拟测试]
+        D1([检出仓库]) --> D2([设置Python])
+        D2 --> D3([下载构建的二进制文件])
+        D3 --> D4([安装PyTest的Python包])
+        D4 --> D5([在WokWi模拟器中运行PyTest])
+        D5 --> D6([上传PyTest结果])
+    end
+
+    D --> E[发布测试应用结果]
+
+    subgraph E[发布测试应用结果]
+        E1([下载测试结果]) --> E2([发布测试结果])
+    end
+
+    classDef startNode fill:#f9f,stroke:#333,stroke-width:4px;
+    class A startNode;
+    classDef subgraphBox fill:#bbf,stroke:#f66,stroke-width:2px,padding:10px;
+    class C,D,E subgraphBox;
+
+```