How can I intergrate ScriptRunner for Jira Cloud with Slack

We can confirm that it is possible to write a Script that would send a notification to Slack but we do not have any examples of how to do this.

In order to achieve this requirement you should review the Slack API documentation located here in order to see what Rest API's you will need to use to achieve this and should contact Slack support located here to ask them any questions that you have on how their third party rest API works.

We have a documentation example located here which shows how you can post a message to Slack and this example may prove a useful reference in helping you to create the script that you require.