Update web.config with .woff mime support

Bootstrap icons aren't visible on Windows Phone because it uses the .woff variant but the mimetype isn't available. Updated the web.config and added .woff to the staticContent section of system.webServer.

src/Umbraco.Web.UI/web.Template.config

@@ -193,6 +193,8 @@
       <mimeMap fileExtension=".air" mimeType="application/vnd.adobe.air-application-installer-package+zip" />
       <remove fileExtension=".svg" />
       <mimeMap fileExtension=".svg" mimeType="image/svg+xml" />
+      <remove fileExtension=".woff"/>
+      <mimeMap fileExtension=".woff" mimeType="application/x-font-woff" />
     </staticContent>
 
     <!-- Ensure the powered by header is not returned -->