Slack platform API and tools docs are now in beta

Today is the day! As previously mentioned, the Slack platform and developer tools documentation are moving: the shiny new Slack platform documentation is now in beta on docs.slack.dev, and the developer tools documentation has fully moved to its new home on tools.slack.dev. The doors are open for our housewarming party 🥳 so come on in, take a look around, and let us know what you think. Thanks for coming along on this journey with us!