Bump nokogiri from 1.10.7 to 1.10.8 in /docs (#133)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.10.7 to 1.10.8.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.10.7...v1.10.8)

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

docs/Gemfile

@@ -8,5 +8,5 @@ gem 'middleman-autoprefixer', '~> 2.7'
 gem 'middleman-sprockets', '~> 4.1'
 gem 'rouge', '~> 2.0.5'
 gem 'redcarpet', '~> 3.4.0'
-gem 'nokogiri', '~> 1.10.4'
+gem 'nokogiri', '~> 1.10.8'
 gem 'sass'

docs/Gemfile.lock

@@ -78,7 +78,7 @@ GEM
       rouge (~> 2.0)
     mini_portile2 (2.4.0)
     minitest (5.13.0)
-    nokogiri (1.10.7)
+    nokogiri (1.10.8)
       mini_portile2 (~> 2.4.0)
     padrino-helpers (0.13.3.4)
       i18n (~> 0.6, >= 0.6.7)
@@ -122,7 +122,7 @@ DEPENDENCIES
   middleman-autoprefixer (~> 2.7)
   middleman-sprockets (~> 4.1)
   middleman-syntax (~> 3.0)
-  nokogiri (~> 1.10.4)
+  nokogiri (~> 1.10.8)
   redcarpet (~> 3.4.0)
   rouge (~> 2.0.5)
   sass