Update Express documentation (5.1.0)

Author: simon04

lib/docs/filters/express/clean_html.rb

@@ -7,14 +7,14 @@ def call
         i += 1 while n && n = n.previous_element
         at_css('h1')['data-level'] = i
 
-        @doc = at_css('#api-doc, .content')
+        @doc = at_css('#api-doc, main, .content')
+
+        css('nav').remove # aria-labelledby="sidebar-heading"
 
         css('section', 'div.highlighter-rouge').each do |node|
           node.before(node.children).remove
         end
 
-        @doc = at_css('#page-doc') unless root_page?
-
         if root_page?
           at_css('h1').remove
           css('> header', '#menu').remove

lib/docs/scrapers/express.rb

@@ -2,9 +2,7 @@ module Docs
   class Express < UrlScraper
     self.name = 'Express'
     self.type = 'express'
-    self.release = '4.21.2'
     self.base_url = 'https://expressjs.com/en/'
-    self.root_path = '4x/api.html'
     self.initial_paths = %w(
       starter/installing.html
       guide/routing.html
@@ -29,6 +27,16 @@ class Express < UrlScraper
       Licensed under the Creative Commons Attribution-ShareAlike License v3.0.
     HTML
 
+    version do
+      self.release = '5.1.0'
+      self.root_path = '5x/api.html'
+    end
+
+    version '4' do
+      self.release = '4.21.2'
+      self.root_path = '4x/api.html'
+    end
+
     def get_latest_version(opts)
       get_npm_version('express', opts)
     end