Link to mdn docs for javascript methods

Add links to mdn docs for event.preventDefault() and event.stopPropagation()

site/content/tutorial/05-events/03-event-modifiers/text.md

@@ -18,8 +18,8 @@ DOM event handlers can have *modifiers* that alter their behaviour. For example,
 
 The full list of modifiers:
 
-* `preventDefault` — calls `event.preventDefault()` before running the handler. Useful for client-side form handling, for example.
+* `preventDefault` — calls [`event.preventDefault()`](https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault) before running the handler. Useful for client-side form handling, for example.
-* `stopPropagation` — calls `event.stopPropagation()`, preventing the event reaching the next element
+* `stopPropagation` — calls [`event.stopPropagation()`](https://developer.mozilla.org/en-US/docs/Web/API/Event/stopPropagation), preventing the event reaching the next element
 * `passive` — improves scrolling performance on touch/wheel events (Svelte will add it automatically where it's safe to do so)
 * `nonpassive` — explicitly set `passive: false`
 * `capture` — fires the handler during the *capture* phase instead of the *bubbling* phase ([MDN docs](https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/Events#Event_bubbling_and_capture))