message: update readme to include opencollective banners
diff: @@ -158,6 +158,21 @@ controller.middleware.send.use(function(bot, message, next) {
  * [Contributing to Botkit Core](CONTRIBUTING.md)
  * [Building platform connectors](https://botkit.ai/docs/howto/build_connector.html)
  +# Support Botkit
  +
  +## Platform Sponsors
  +
  +<object type="image/svg+xml" data="https://opencollective.com/botkit/tiers/platform-sponsor.svg?avatarHeight=36&width=600"></object>
  +
  +## Corporate Sponsors
  +
  +<object type="image/svg+xml" data="https://opencollective.com/botkit/tiers/corporate-sponsor.svg?avatarHeight=36&width=600"></object>
  +
  +## Individual Contributors
  +
  +<object type="image/svg+xml" data="https://opencollective.com/botkit/tiers/individual-sponsor.svg?avatarHeight=36&width=600"></object>
  +
  +
  # Community & Support
  Join our thriving community of Botkit developers and bot enthusiasts at large.
  