Disable crawling on Netlify. (#29193)

Gruntfile.js

diff --git a/Gruntfile.js b/Gruntfile.js
index 39ba49a..43f923f 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -291,7 +291,7 @@
       docs: {},
       netlify: {
         options: {
-          raw: 'github: true\nbaseurl: ""'
+          raw: 'github: true\nbaseurl: ""\nnetlify: true'
         }
       },
       github: {

docs/robots.txt

diff --git a/docs/robots.txt b/docs/robots.txt
index aef3fa1..c68014e 100644
--- a/docs/robots.txt
+++ b/docs/robots.txt
@@ -3,7 +3,9 @@
 
 # www.robotstxt.org/
 
+{% if site.netlify != true and site.github == true -%}
 # Allow crawling of all content
+{%- endif %}
 User-agent: *
-Disallow:
+Disallow:{% if site.netlify == true or site.github != true %} /{% endif %}
 Sitemap: {{ site.url }}/sitemap.xml