feat: Enhance SEO and accessibility for website

- Updated title and meta tags in index.html for better search engine optimization.
- Added Open Graph and Twitter Card metadata for improved social media sharing.
- Included structured data for the game server in index.html.
- Improved accessibility with a skip link to main content in index.html.
- Enhanced player stats page (stats.html) with additional meta tags and structured data.
- Created robots.txt to manage web crawler access and included sitemap reference.
- Added sitemap.xml with URLs for the homepage and player stats page.
- Removed pigwei.html as it is no longer needed.

sitemap.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
+        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9
+        http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd">
+    
+    <!-- 首页 -->
+    <url>
+        <loc>https://mcpure.lunadeer.cn/</loc>
+        <lastmod>2026-02-11</lastmod>
+        <changefreq>weekly</changefreq>
+        <priority>1.0</priority>
+    </url>
+    
+    <!-- 玩家数据页 -->
+    <url>
+        <loc>https://mcpure.lunadeer.cn/stats.html</loc>
+        <lastmod>2026-02-11</lastmod>
+        <changefreq>daily</changefreq>
+        <priority>0.8</priority>
+    </url>
+    
+</urlset>