readded hugo-book theme files.

themes/hugo-book/layouts/_partials/docs/text/template.html

@@ -0,0 +1,9 @@
+<!--
+  Returns rendered string from template and context.
+  Usage: partial "docs/string-template" (dict "Template" "param={{ . }}" "Context" "Input")
+-->
+
+{{- $checksum := . | encoding.Jsonify | crypto.SHA1 | printf "book-%s" -}}
+{{- $template := resources.FromString $checksum .Template -}}
+{{- $template = $template | resources.ExecuteAsTemplate $checksum .Context -}}
+{{- return $template.Content -}}