Generate a sitemap for docs.bazel.build

Closes #10983.

PiperOrigin-RevId: 301686893
diff --git a/scripts/docs/Gemfile b/scripts/docs/Gemfile
index 9f812cc..6512903 100644
--- a/scripts/docs/Gemfile
+++ b/scripts/docs/Gemfile
@@ -1,5 +1,6 @@
-gem 'jekyll', '3.8.6'
+gem 'jekyll', '~> 3.8.6'
 gem 'jekyll-paginate', '~> 1.0'
 gem 'pygments.rb', '~> 0.6.0'
 gem 'redcarpet', '~> 3.2', '>= 3.2.3'
 gem 'jekyll-toc', '~> 0.13.1'
+gem 'jekyll-sitemap', '~> 1.4.0'
diff --git a/site/_config.yml b/site/_config.yml
index 630b1e4..db12e0e 100644
--- a/site/_config.yml
+++ b/site/_config.yml
@@ -11,6 +11,9 @@
 gems:
   - jekyll-paginate
   - jekyll-toc
+  - jekyll-sitemap
+
+url: "https://docs.bazel.build" # used by jekyll-sitemap
 
 # Update this to the newest release for the default docs.bazel.build version.
 version: "2.2.0"
@@ -52,6 +55,7 @@
       path: ""
     values:
       toc: true
+      sitemap: true
 
 # jekyll-toc settings
 toc:
diff --git a/site/_includes/footer-content.html b/site/_includes/footer-content.html
index 9d7a9f1..9485ca4 100644
--- a/site/_includes/footer-content.html
+++ b/site/_includes/footer-content.html
@@ -8,6 +8,7 @@
         <li><a href="{{ site.main_site_url }}/contributing.html">Contribute</a></li>
         <li><a href="{{ site.main_site_url }}/governance.html">Governance Plan</a></li>
         <li><a href="https://policies.google.com/privacy">Privacy Policy</a></li>
+        <li><a href="{{ site.docs_site_url }}/sitemap.xml">Sitemap</a></li>
       </ul>
     </div>
     <div class="col-sm-4 col-md-2">