Enable index, follow in the production website

The website header partial sets the meta index, follow if the
HUGO_ENV is set to production, and no index no follow otherwise.

Change the HUGO_ENV to be production for the production environment.

Related to #191
Signed-off-by: NAndrea Frittoli <andrea.frittoli@gmail.com>

netlify.toml

@@ -5,11 +5,17 @@
 [build.environment]
   HUGO_VERSION = "0.53"
 
-[dev]
-  command = "make serve URL=http://localhost:8888/"
+[context.production.environment]
+  HUGO_ENV = "production"
 
 [context.deploy-preview]
+  HUGO_ENV = "staging"
   command = "make preview-build"
 
 [context.branch-deploy]
   command = "make preview-build"
+
+
+
+[dev]
+  command = "make serve URL=http://localhost:8888/"
\ No newline at end of file