feat(content): add description to index files

Added a description field to both English and Chinese index files to provide additional context about the content.

Author: geekifan

exampleSite/content/_index.md

@@ -1,5 +1,7 @@
 ---
 title: "Lorem ipsum"
+description: >-
+  Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus ornare aliquet ipsum, ac tempus justo dapibus sit amet. Suspendisse condimentum, libero vel tempus mattis, risus risus vulputate libero, elementum fermentum mi neque vel nisl. Maecenas facilisis maximus dignissim.
 ---
 
 # About Me {#about-me}

exampleSite/content/_index.zh.md

@@ -1,5 +1,7 @@
 ---
 title: "王小明"
+description: >-
+  我是王小明，目前专注于自然语言处理和计算机视觉领域的研究。我的研究兴趣包括神经机器翻译、图像生成和多模态学习。
 ---
 
 # 关于我 {#about-me}