docs: fix multiple typos in customization chapters (#10727)

www/apps/book/app/learn/customization/integrate-systems/handle-event/page.mdx

@@ -45,7 +45,7 @@ export const eventHighlights = [
   ["15", "data", "The data to pass in the payload."]
 ]
 
-```ts title="src/workflows/create-brand/index.ts" highlights={eventHighlights}
+```ts title="src/workflows/create-brand.ts" highlights={eventHighlights}
 // other imports...
 import { 
   emitEventStep,