Include CircleCI workflow name in Slack message

[devatherock]

Multiple slack notifications might be triggered from different workflows within the same pipeline. Including the workflow name in the message would help differentiate them. Below is what the messages from different workflows look like now:

The workflow name is present in the name field of the CircleCI workflow API response. Sample response below:

{
  "pipeline_id" : "a4a66555-3b52-401e-a7ed-e7a2f4cee910",
  "id" : "cd47d758-b3c4-4c66-8528-2e2ea21aac1d",
  "name" : "release_plugin",
  "project_slug" : "gh/devatherock/simple-slack",
  "status" : "success",
  "started_by" : "8818d349-2523-4da8-a0fa-6cda8f303973",
  "pipeline_number" : 234,
  "created_at" : "2024-06-07T07:00:32Z",
  "stopped_at" : "2024-06-07T07:00:59Z"
}