Update extensions.yml
Update extensions.yml

Add middleman-sitemap
dhulihan/middleman-directory,krautcomputing/middleman-directory,natbatwat/middleman-directory,middleman/middleman-directory,dhulihan/middleman-directory,krautcomputing/middleman-directory,pzi/middleman-directory,middleman/middleman-directory,dhulihan/middleman-directory,natbatwat/middleman-directory,middleman/middleman-directory,pzi/middleman-directory,krautcomputing/middleman-directory,pzi/middleman-directory,natbatwat/middleman-directory