Feature: Slack - receive messages, create threads, send replies (#974)

Co-authored-by: Pranav Raj S <pranav@thoughtwoot.com>

.env.example

@@ -59,6 +59,7 @@ MANDRILL_INGRESS_API_KEY=
 ACTIVE_STORAGE_SERVICE=local
 
 # Amazon S3
+# documentation: https://www.chatwoot.com/docs/configuring-s3-bucket-as-cloud-storage
 S3_BUCKET_NAME=
 AWS_ACCESS_KEY_ID=
 AWS_SECRET_ACCESS_KEY=
@@ -74,20 +75,23 @@ LOG_LEVEL=info
 LOG_SIZE=500
 
 ### This environment variables are only required if you are setting up social media channels
-#facebook
+
+# Facebook
+# documentation: https://www.chatwoot.com/docs/facebook-setup
 FB_VERIFY_TOKEN=
 FB_APP_SECRET=
 FB_APP_ID=
 
 # Twitter
+# documentation: https://www.chatwoot.com/docs/twitter-app-setup
 TWITTER_APP_ID=
 TWITTER_CONSUMER_KEY=
 TWITTER_CONSUMER_SECRET=
 TWITTER_ENVIRONMENT=
 
-#slack
+#slack integration
 SLACK_CLIENT_ID=
-SLACK_CLIENT_SECRET
+SLACK_CLIENT_SECRET=
 
 ### Change this env variable only if you are using a custom build mobile app
 ## Mobile app env variables