Update Express documentation (5.2.1)

Author: simon04

lib/docs/filters/express/clean_html.rb

@@ -39,6 +39,7 @@ def call
 
         css('pre > code').each do |node|
           node.parent['data-language'] = node['class'][/language-(\w+)/, 1] if node['class']
+          node.parent['data-language'] ||= 'javascript'
           node.parent.content = node.parent.content
         end
 

lib/docs/scrapers/express.rb

@@ -28,7 +28,7 @@ class Express < UrlScraper
     HTML
 
     version do
-      self.release = '5.1.0'
+      self.release = '5.2.1'
       self.root_path = '5x/api.html'
     end