style: 文档样式细节修改 (#504)

src/sites/assets/styles/md-style.scss

@@ -210,6 +210,7 @@
     padding: 16px;
     background-color: #fff4f0;
     border-left: 6px solid #fa192c;
+    border-radius: 3px;
     p {
       color: #1a1a1a;
     }