Merge pull request howdyai#1981 from raycharius/patch-1

Add Block Kit library links to README

packages/botbuilder-adapter-slack/readme.md

@@ -239,6 +239,11 @@ Botkit will automatically construct your outgoing messages according to Slack's
 
 The preferred way of composing interactive messages is using Slack's Block Kit.  [Read the official Slack documentation here](https://api.slack.com/messaging/composing/layouts). Slack provides a UI to help create your interactive messages. Check out [Block Kit Builder](https://api.slack.com/tools/block-kit-builder).
 
+Additionally, there are open-source libraries available that assist with building out UIs for Slack:
+
+* [**Block Builder**](https://github.com/raycharius/slack-block-builder) – Zero-dependency library, with a SwiftUI-like builder syntax.
+* [**JSX-Slack**](https://github.com/speee/jsx-slack) – JSX that transpiles to Slack API-compatible JSON.
+
 Interactive messages using blocks can be sent via any of Botkit's built in functions by passing in the appropriate "blocks" as part of the message.  Here is an example:
 
 ```javascript