build(deps-dev): bump html-proofer from 3.18.2 to 3.18.5 in /docs

Bumps [html-proofer](https://github.com/gjtorikian/html-proofer) from 3.18.2 to 3.18.5.
- [Release notes](https://github.com/gjtorikian/html-proofer/releases)
- [Commits](https://github.com/gjtorikian/html-proofer/compare/v3.18.2...v3.18.5

)

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

docs/Gemfile.lock

@@ -28,7 +28,7 @@ GEM
     execjs (2.7.0)
     faraday (1.0.1)
       multipart-post (>= 1.2, < 3)
-    ffi (1.14.1)
+    ffi (1.14.2)
     forwardable-extended (2.6.0)
     gemoji (3.0.1)
     github-pages (209)
@@ -84,7 +84,7 @@ GEM
     html-pipeline (2.14.0)
       activesupport (>= 2)
       nokogiri (>= 1.4)
-    html-proofer (3.18.2)
+    html-proofer (3.18.5)
       addressable (~> 2.3)
       mercenary (~> 0.3)
       nokogumbo (~> 2.0)
@@ -210,15 +210,16 @@ GEM
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
     mercenary (0.3.6)
-    mini_portile2 (2.4.0)
+    mini_portile2 (2.5.0)
     minima (2.5.1)
       jekyll (>= 3.5, < 5.0)
       jekyll-feed (~> 0.9)
       jekyll-seo-tag (~> 2.1)
     minitest (5.14.2)
     multipart-post (2.1.1)
-    nokogiri (1.10.10)
-      mini_portile2 (~> 2.4.0)
+    nokogiri (1.11.0)
+      mini_portile2 (~> 2.5.0)
+      racc (~> 1.4)
     nokogumbo (2.0.4)
       nokogiri (~> 1.8, >= 1.8.4)
     octokit (4.18.0)
@@ -228,6 +229,7 @@ GEM
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     public_suffix (3.1.1)
+    racc (1.5.2)
     rainbow (3.0.0)
     rake (13.0.3)
     rb-fsevent (0.10.4)