Migrate docs.bazel.build to use GitHub Flavored Markdown instead of Kramdown, attempt #2

Rollforward after redirect pages have been fixed by https://github.com/bazelbuild/bazel/commit/565f7742d584588bd3b329ce7303bd2673b3a284. Fixes https://github.com/bazelbuild/bazel/issues/11451

RELNOTES:
PiperOrigin-RevId: 314288440
diff --git a/scripts/docs/Gemfile b/scripts/docs/Gemfile
index 6512903..02e8458 100644
--- a/scripts/docs/Gemfile
+++ b/scripts/docs/Gemfile
@@ -4,3 +4,7 @@
 gem 'redcarpet', '~> 3.2', '>= 3.2.3'
 gem 'jekyll-toc', '~> 0.13.1'
 gem 'jekyll-sitemap', '~> 1.4.0'
+
+group :jekyll_plugins do
+  gem 'jekyll-commonmark-ghpages', '~> 0.1.6'
+end
diff --git a/site/_config.yml b/site/_config.yml
index dade643..7ba7fd1 100644
--- a/site/_config.yml
+++ b/site/_config.yml
@@ -1,5 +1,5 @@
 destination: production
-markdown: kramdown
+markdown: CommonMarkGhPages
 kramdown:
   syntax_highlighter: rouge
   toc_levels: "2,3"
@@ -12,6 +12,7 @@
   - jekyll-paginate
   - jekyll-toc
   - jekyll-sitemap
+  - jekyll-commonmark-ghpages
 
 url: "https://docs.bazel.build" # used by jekyll-sitemap
 
@@ -66,3 +67,7 @@
   max_level: 3
   list_class: page-toc
   sublist_class: page-toc-sublist
+
+commonmark:
+  options: ["SMART", "FOOTNOTES"]
+  extensions: ["strikethrough", "autolink", "table", "tagfilter"]