[docs] explain initial value for bind scroll (#7065)

Co-authored-by: Ben McCann <322311+benmccann@users.noreply.github.com>

site/content/docs/02-template-syntax.md

@@ -1671,6 +1671,7 @@ All except `scrollX` and `scrollY` are readonly.
 <svelte:window bind:scrollY={y}/>
 ```
 
+> Note that the page will not be scrolled to the initial value to avoid accessibility issues. Only subsequent changes to the bound variable of `scrollX` and `scrollY` will cause scrolling. However, if the scrolling behaviour is desired, call `scrollTo()` in `onMount()`.
 
 ### `<svelte:body>`