feat(docker): Serve a robots.txt file for NO indexing

ref: #756

app/project-static/robots.txt

@@ -0,0 +1,2 @@
+User-agent: *
+Disallow: /

includes/etc/nginx/conf.d/centurion.conf

@@ -4,6 +4,10 @@ server {
 
     location = /favicon.ico { access_log off; log_not_found off; }
 
+    location /robots.txt {
+        alias /app/static/robots.txt;
+    }
+
     location /static/ {
 
         alias /app/static/;