(doc) update deps

docs/Gemfile

@@ -25,3 +25,5 @@ gem "wdm", "~> 0.1.0" if Gem.win_platform?
 
 
 gem "webrick", "~> 1.7"
+
+gem "html-pipeline", "2.4.1"

docs/Gemfile.lock

@@ -1,9 +1,11 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (3.2.22.5)
-      i18n (~> 0.6, >= 0.6.4)
-      multi_json (~> 1.0)
+    activesupport (4.2.11.3)
+      i18n (~> 0.7)
+      minitest (~> 5.1)
+      thread_safe (~> 0.3, >= 0.3.4)
+      tzinfo (~> 1.1)
     addressable (2.7.0)
       public_suffix (>= 2.0.2, < 5.0)
     coffee-script (2.4.1)
@@ -81,8 +83,8 @@ GEM
       octokit (~> 4.0)
       public_suffix (~> 3.0)
       typhoeus (~> 1.3)
-    html-pipeline (2.14.0)
-      activesupport (>= 2)
+    html-pipeline (2.4.1)
+      activesupport (>= 2, < 5)
       nokogiri (>= 1.4)
     http_parser.rb (0.6.0)
     i18n (0.9.5)
@@ -206,7 +208,7 @@ GEM
       jekyll (>= 3.5, < 5.0)
       jekyll-feed (~> 0.9)
       jekyll-seo-tag (~> 2.1)
-    multi_json (1.15.0)
+    minitest (5.14.3)
     multipart-post (2.1.1)
     nokogiri (1.11.1-x64-mingw32)
       racc (~> 1.4)
@@ -239,10 +241,11 @@ GEM
       unf (~> 0.1.4)
     terminal-table (1.8.0)
       unicode-display_width (~> 1.1, >= 1.1.1)
+    thread_safe (0.3.6)
     typhoeus (1.4.0)
       ethon (>= 0.9.0)
-    tzinfo (2.0.4)
-      concurrent-ruby (~> 1.0)
+    tzinfo (1.2.9)
+      thread_safe (~> 0.1)
     tzinfo-data (1.2021.1)
       tzinfo (>= 1.0.0)
     unf (0.1.4)
@@ -257,10 +260,11 @@ PLATFORMS
 
 DEPENDENCIES
   github-pages
+  html-pipeline (= 2.4.1)
   jekyll-theme-architect
   tzinfo-data
   wdm (~> 0.1.0)
   webrick (~> 1.7)
 
 BUNDLED WITH
-   2.2.3
+   2.2.8