Add mattermost to the list
Add mattermost to the list

PropertyUX/nubot,hubotio/hubot,ouadie-lahdioui/hubot,decaffeinate-examples/hubot,hubotio/hubot,PropertyUX/nubot,WaleedAshraf/hubot,skcript/skubot,decaffeinate-examples/hubot,lisb/hubot,Mattlk13/Hubot,github/hubot,ClaudeBot/hubot,mrb/hubot,makii42/hubot,pchaigno/hubot,nandub/hubot,nandub/hubot,scboucher/hubot,ddmng/brazil82-hubot,lisb/hubot,zvelo/hubot,rlugojr/hubot,lisb/hubot,github/hubot,scboucher/hubot