improve robots to use site param

layouts/robots.txt

@@ -1,6 +1,6 @@
 User-agent: *
 # robotstxt.org - if ENV production variable is false robots will be disallowed.
-{{ if eq (getenv "HUGO_ENV") "production" }}
+{{ if eq (getenv "HUGO_ENV") "production" | or (eq .Site.Params.env "production")  }}
   Disallow:
 {{ else }}
   Disallow: /