Update index.md

Author: christophsanz

apps/svelte.dev/content/tutorial/02-advanced-svelte/04-advanced-bindings/04-dimensions/index.md

@@ -13,3 +13,7 @@ You can add `clientWidth`, `clientHeight`, `offsetWidth` and `offsetHeight` bind
 ```
 
 These bindings are readonly — changing the values of `w` and `h` won't have any effect on the element.
+
+> [!NOTE] Elements are measured using a technique similar to [this one](http://www.backalleycoder.com/2013/03/18/cross-browser-event-based-element-resize-detection/). There is some overhead involved, so it's not recommended to use this for large numbers of elements.
+>
+> `display: inline` elements cannot be measured with this approach; nor can elements that can't contain other elements (such as `<canvas>`). In these cases you will need to measure a wrapper element instead.