Bump sanitize from 4.4.0 to 5.2.1 in /site/jekyll (#1122)

Bumps [sanitize](https://github.com/rgrove/sanitize) from 4.4.0 to 5.2.1.
- [Release notes](https://github.com/rgrove/sanitize/releases)
- [Changelog](https://github.com/rgrove/sanitize/blob/master/HISTORY.md)
- [Commits](rgrove/sanitize@v4.4.0...v5.2.1)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

site/jekyll/Gemfile.lock

@@ -10,7 +10,7 @@ GEM
     colorator (0.1)
     commander (4.1.6)
       highline (~> 1.6.11)
-    crass (1.0.2)
+    crass (1.0.6)
     fast-stemmer (1.0.2)
     ffi (1.9.18)
     ffi (1.9.18-x64-mingw32)
@@ -41,12 +41,12 @@ GEM
     maruku (0.7.0)
     mini_portile2 (2.4.0)
     multi_json (1.12.1)
-    nokogiri (1.10.8)
+    nokogiri (1.10.9)
       mini_portile2 (~> 2.4.0)
-    nokogiri (1.10.8-x64-mingw32)
+    nokogiri (1.10.9-x64-mingw32)
       mini_portile2 (~> 2.4.0)
-    nokogumbo (1.4.10)
-      nokogiri
+    nokogumbo (2.0.2)
+      nokogiri (~> 1.8, >= 1.8.4)
     parslet (1.5.0)
       blankslate (~> 2.0)
     posix-spawn (0.3.13)
@@ -61,10 +61,10 @@ GEM
       ffi (>= 0.5.0)
     redcarpet (2.3.0)
     safe_yaml (1.0.4)
-    sanitize (4.4.0)
+    sanitize (5.2.1)
       crass (~> 1.0.2)
-      nokogiri (>= 1.4.4)
-      nokogumbo (~> 1.4.1)
+      nokogiri (>= 1.8.0)
+      nokogumbo (~> 2.0)
     sass (3.4.23)
     sprockets (2.12.4)
       hike (~> 1.2)