feat(WorkflowAdd): 为表单按钮添加图标和间距优化

在工作流添加页面的表单底部，为"发布工作流"和"取消"按钮添加了图标，
并使用适当的间距来改善视觉效果和用户体验。

src/pages/WorkflowAdd.vue

@@ -83,8 +83,14 @@
         </el-form-item>
       </div>
       <div class="mt20">
-        <el-button type="primary" class="font_size16" @click="submitForm">发布工作流</el-button>
-        <el-button class="font_size16" @click="goBack">取消</el-button>
+        <el-button type="primary" class="font_size16" @click="submitForm">
+          <el-icon><Promotion /></el-icon>
+          <span class="ml10">发布工作流</span>
+        </el-button>
+        <el-button class="font_size16" @click="goBack">
+          <el-icon><Close /></el-icon>
+          <span class="ml10">取消</span>
+        </el-button>
       </div>
     </el-form>
   </div>