Update Cmake to 3.20

lib/docs/scrapers/cmake.rb

@@ -16,10 +16,15 @@ module Docs
     options[:skip_patterns] = [/\Agenerator/, /\Acpack_gen/, /\Ainclude/, /\Arelease/]
 
     options[:attribution] = <<-HTML
-      &copy; 2000&ndash;2020 Kitware, Inc. and Contributors<br>
+      &copy; 2000&ndash;2021 Kitware, Inc. and Contributors<br>
       Licensed under the BSD 3-clause License.
     HTML
 
+    version '3.20' do
+      self.release = '3.20'
+      self.base_url = "https://cmake.org/cmake/help/v#{self.version}/"
+    end
+
     version '3.19' do
       self.release = '3.19.0'
       self.base_url = "https://cmake.org/cmake/help/v#{self.version}/"