Put metadata tags into partial

And update example config.toml (relate to #40)

exampleSite/config.toml

@@ -17,7 +17,9 @@ enableEmoji = true  # Shorthand emojis in content files - https://gohugo.io/func
   name = "John Doe"
 
 [blackfriday]
-  hrefTargetBlank = true
+  # hrefTargetBlank = true
+  # noreferrerLinks = true
+  # nofollowLinks = true
 
 [taxonomies]
   tag = "tags"

layouts/_default/baseof.html

@@ -9,9 +9,7 @@
 	<meta name="theme-color" content="{{.}}">
 	<meta name="msapplication-TileColor" content="{{.}}">
 	{{- end }}
-	{{- template "_internal/schema.html" . }}
-	{{- template "_internal/opengraph.html" . }}
-	{{- template "_internal/twitter_cards.html" . }}
+	{{- partial "structured-data.html" . }}
 	{{- partial "favicons.html" }}
 	<title>{{.Title}}</title>
 	{{ range .AlternativeOutputFormats -}}

layouts/partials/structured-data.html

@@ -0,0 +1,6 @@
+{{/* We use some Hugo built-in templates, you can find their source here: */}}
+{{/* https://github.com/gohugoio/hugo/tree/master/tpl/tplimpl/embedded/templates */}}
+
+{{- template "_internal/schema.html" . }}
+{{- template "_internal/opengraph.html" . }}
+{{- template "_internal/twitter_cards.html" . }}