Add button for showing the manual (#4)

index.html

@@ -33,7 +33,7 @@ <h2>ein <span class="primary">Typst</span> Zeichenpaket</h2>
           <p>A Typst drawing package by Johannes Wolf and fenjalien</p>
           <div class="header-buttons">
             <a
-              href="https://cetz-package.github.io/docs/overview.html"
+              href="https://cetz-package.github.io/docs"
               class="solid"
               target="_blank"
               >Go to Docs</a