Fix title tag on landing page

Author: maartenba

src/content/docs/index.mdx

@@ -1,5 +1,8 @@
 ---
 title: Duende Software<br/> Docs
+head:
+  - tag: title
+    content: Duende Software Docs
 description: Get started building your .NET applications with IdentityServer, Backend-for-Frontend (BFF) and our open-source tools.
 template: splash
 giscus: false