Bump github-pages from 186 to 187 in /docs

Bumps [github-pages](https://github.com/github/pages-gem) from 186 to 187.
- [Release notes](https://github.com/github/pages-gem/releases)
- [Commits](https://github.com/github/pages-gem/compare/v186...v187

)

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

docs/Gemfile.lock

@@ -26,10 +26,10 @@ GEM
     execjs (2.7.0)
     faraday (0.15.2)
       multipart-post (>= 1.2, < 3)
-    ffi (1.9.23)
+    ffi (1.9.25)
     forwardable-extended (2.6.0)
     gemoji (3.0.0)
-    github-pages (186)
+    github-pages (187)
       activesupport (= 4.2.10)
       github-pages-health-check (= 1.8.1)
       jekyll (= 3.7.3)
@@ -48,7 +48,7 @@ GEM
       jekyll-relative-links (= 0.5.3)
       jekyll-remote-theme (= 0.3.1)
       jekyll-sass-converter (= 1.5.2)
-      jekyll-seo-tag (= 2.4.0)
+      jekyll-seo-tag (= 2.5.0)
       jekyll-sitemap (= 1.2.0)
       jekyll-swiss (= 0.4.0)
       jekyll-theme-architect (= 0.1.1)
@@ -80,7 +80,7 @@ GEM
       octokit (~> 4.0)
       public_suffix (~> 2.0)
       typhoeus (~> 1.3)
-    html-pipeline (2.8.0)
+    html-pipeline (2.8.3)
       activesupport (>= 2)
       nokogiri (>= 1.4)
     http_parser.rb (0.6.0)
@@ -138,7 +138,7 @@ GEM
       rubyzip (>= 1.2.1, < 3.0)
     jekyll-sass-converter (1.5.2)
       sass (~> 3.4)
-    jekyll-seo-tag (2.4.0)
+    jekyll-seo-tag (2.5.0)
       jekyll (~> 3.3)
     jekyll-sitemap (1.2.0)
       jekyll (~> 3.3)
@@ -206,7 +206,7 @@ GEM
       jekyll-seo-tag (~> 2.1)
     minitest (5.11.3)
     multipart-post (2.0.0)
-    nokogiri (1.8.2)
+    nokogiri (1.8.3)
       mini_portile2 (~> 2.3.0)
     octokit (4.9.0)
       sawyer (~> 0.8.0, >= 0.5.3)
@@ -237,7 +237,7 @@ GEM
       ethon (>= 0.9.0)
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
-    unicode-display_width (1.3.3)
+    unicode-display_width (1.4.0)
 
 PLATFORMS
   ruby