Add Block Kit title

src/format.rs

@@ -154,6 +154,14 @@ mod slack_tests {
             body,
             json!({
                 "blocks": [
+                    {
+                        "type": "header",
+                        "text": {
+                            "type": "plain_text",
+                            "text": "Changes detected in the shop",
+                            "emoji": true
+                        }
+                    },
                     {
                         "type": "section",
                         "text": {