Fix missing entries in Python doc

Fixes #463.

lib/docs/filters/python/entries_v2.rb

@@ -67,7 +67,7 @@ module Docs
           end
         end
 
-        css('.function > dt[id]', '.method > dt[id]', '.classmethod > dt[id]').each do |node|
+        css('.function > dt[id]', '.method > dt[id]', '.staticmethod > dt[id]', '.classmethod > dt[id]').each do |node|
           entries << [node['id'] + '()', node['id']]
         end
 

lib/docs/filters/python/entries_v3.rb

@@ -63,7 +63,7 @@ module Docs
           end
         end
 
-        css('.function > dt[id]', '.method > dt[id]', '.classmethod > dt[id]').each do |node|
+        css('.function > dt[id]', '.method > dt[id]', '.staticmethod > dt[id]', '.classmethod > dt[id]').each do |node|
           entries << [node['id'] + '()', node['id']]
         end