docs: Add spread guidance for multiple event handlers (#13240)

* Update 04-event-handlers.md

Added documentation on managing multiple event handlers and spreading props.

* Update 04-event-handlers.md

Used spread variable rather than implying there was a props variable from $props above.

* tweak

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

sites/svelte-5-preview/src/routes/docs/content/01-api/04-event-handlers.md

@@ -178,6 +178,20 @@ Duplicate attributes/properties on elements — which now includes event handler
 </button>
 ```
 
+When spreading props, local event handlers must go _after_ the spread, or they risk being overwritten:
+
+```svelte
+<button
+	{...props}
+	onclick={(e) => {
+		doStuff(e);
+		props.onclick?.(e);
+	}}
+>
+	...
+</button>
+```
+
 ## Why the change?
 
 By deprecating `createEventDispatcher` and the `on:` directive in favour of callback props and normal element properties, we: