Update HAProxy documentation (2.9.0)

Author: simon04

lib/docs/scrapers/haproxy.rb

@@ -20,6 +20,11 @@ class Haproxy < UrlScraper
       Licensed under the GNU General Public License version 2.
     HTML
 
+    version '2.9' do
+      self.release = '2.9.0'
+      self.base_url = "https://docs.haproxy.org/#{self.version}/"
+    end
+
     version '2.8' do
       self.release = '2.8.0'
       self.base_url = "https://docs.haproxy.org/#{self.version}/"