👍update changelog entry to include instructions for upgrade

Signed-off-by: Charles Lowell <cowboyd@frontside.com>

.changeset/rotten-colts-decide.md

@@ -2,4 +2,37 @@
 '@backstage/plugin-catalog-backend-module-incremental-ingestion': minor
 ---
 
-Allow incremental event handlers to be async; Force event handler to indicate if it made a change
+**BREAKING** Allow incremental event handlers to be async; Force event handler
+to indicate if it made a change. Instead of returning `null` or `undefined` from an event
+handler to indicate no-oop, instead return the value { type: "ignored" }.
+
+**before**
+
+```javascript
+import { createDelta, shouldIgnore } from "./my-delta-creater";
+
+eventHandler: {
+  onEvent(params) {
+    if (shouldIgnore(params)) {
+      return;
+    }
+    return createDelta(params);
+  }
+}
+```
+
+**after**
+
+```javascript
+import { createDelta, shouldIgnore } from "./my-delta-creater";
+
+eventHandler: {
+  async onEvent(params) {
+    if (shouldIgnore(params) {
+      return { type: "ignored" };
+    }
+    // code to create delta can now be async if needed
+    return await createDelta(params);
+  }
+}
+```