Bump nokogiri from 1.10.1 to 1.10.4 in /docs

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.10.1 to 1.10.4.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sparklemotion/nokogiri/compare/v1.10.1...v1.10.4)

Signed-off-by: dependabot[bot] <support@github.com>

docs/Gemfile.lock

@@ -23,10 +23,12 @@ GEM
       http_parser.rb (~> 0.6.0)
     ethon (0.12.0)
       ffi (>= 1.3.0)
+    eventmachine (1.2.7)
     eventmachine (1.2.7-x64-mingw32)
     execjs (2.7.0)
     faraday (0.15.4)
       multipart-post (>= 1.2, < 3)
+    ffi (1.10.0)
     ffi (1.10.0-x64-mingw32)
     forwardable-extended (2.6.0)
     gemoji (3.0.0)
@@ -205,7 +207,9 @@ GEM
       jekyll-seo-tag (~> 2.1)
     minitest (5.11.3)
     multipart-post (2.0.0)
-    nokogiri (1.10.1-x64-mingw32)
+    nokogiri (1.10.4)
+      mini_portile2 (~> 2.4.0)
+    nokogiri (1.10.4-x64-mingw32)
       mini_portile2 (~> 2.4.0)
     octokit (4.13.0)
       sawyer (~> 0.8.0, >= 0.5.3)
@@ -239,6 +243,7 @@ GEM
     unicode-display_width (1.4.1)
 
 PLATFORMS
+  ruby
   x64-mingw32
 
 DEPENDENCIES