Update donate link in index.html

docs/index.html

@@ -87,7 +87,7 @@
                 </div>
             </div>
             <a class="item" href="./document/">Document•文档</a>
-            <a class="item" href="./donate/">Donate•捐助</a>
+            <a class="item" href="./donate.html">Donate•捐助</a>
             <a class="item" href="https://github.com/zhw2590582/ArtPlayer">Github</a>
         </div>
         <div class="tool">