Update index.rst

Fixing style guide link

docs/index.rst

@@ -62,7 +62,7 @@ Contribute
 **We accept pull requests!** But you're more likely to have yours accepted if you follow these guidelines:
 
 	1. Read https://github.com/aspnet/Docs/blob/master/CONTRIBUTING.md
-	2. Follow the `ASP.NET Docs Style Guide <contribute/style-guide/style-guide>`_
+	2. Follow the `ASP.NET Docs Style Guide <contribute/style-guide/style-guide.html>`_
 
 .. Indices and tables
 .. ==================