Add info about modifying throttle duration (#2443)

Just added some info confirming that `.throttle` can use the same duration modifier as `.debounce`. This functionality was implied by throttle's similarity to 'debounce', but now it's explicitly mentioned, avoiding any confusion.

packages/docs/src/en/directives/on.md

@@ -234,6 +234,14 @@ The above example is a great use case of throttling. Without `.throttle`, the `h
 
 > Fun Fact: This exact strategy is used on this very documentation site to update the currently highlighted section in the right sidebar.
 
+Just like with `.debounce`, you can add a custom duration to your throttled event:
+
+```alpine
+<div @scroll.window.throttle.750ms="handleScroll">...</div>
+```
+
+Now, `handleScroll` will only be called every 750 milliseconds.
+
 <a name="self"></a>
 ### .self