Capitalize "Slack" across the README
Capitalize "Slack" across the README

risdhillon/slack_demo,outsideris/slack-invite-automation,jonathanon/slackcommunityinvite,dhaula/slack-auto-join,outsideris/slack-invite-automation,jonathanon/slackcommunityinvite,dhaula/slack-auto-join,patrickdaniel/slack-invite-automation,risdhillon/slack_demo,ultias/globaltradingmarket,ultias/globaltradingmarket,Doken-Tokuyama/slack-invite,Doken-Tokuyama/slack-invite,outsideris/slack-invite-automation,patrickdaniel/slack-invite-automation