Bump html-proofer from 3.15.1 to 3.15.2

Bumps [html-proofer](https://github.com/gjtorikian/html-proofer) from 3.15.1 to 3.15.2.
- [Release notes](https://github.com/gjtorikian/html-proofer/releases)
- [Commits](gjtorikian/html-proofer@v3.15.1...v3.15.2)

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

Author: dependabot-preview[bot]

Gemfile.lock

@@ -11,9 +11,9 @@ GEM
     ethon (0.12.0)
       ffi (>= 1.3.0)
     eventmachine (1.2.7)
-    ffi (1.12.1)
+    ffi (1.12.2)
     forwardable-extended (2.6.0)
-    html-proofer (3.15.1)
+    html-proofer (3.15.2)
       addressable (~> 2.3)
       mercenary (~> 0.3)
       nokogumbo (~> 2.0)
@@ -53,7 +53,7 @@ GEM
       ruby_dep (~> 1.2)
     mercenary (0.3.6)
     mini_portile2 (2.4.0)
-    nokogiri (1.10.8)
+    nokogiri (1.10.9)
       mini_portile2 (~> 2.4.0)
     nokogumbo (2.0.2)
       nokogiri (~> 1.8, >= 1.8.4)
@@ -75,7 +75,7 @@ GEM
       rb-inotify (~> 0.9, >= 0.9.7)
     typhoeus (1.3.1)
       ethon (>= 0.9.0)
-    yell (2.2.1)
+    yell (2.2.2)
 
 PLATFORMS
   ruby