note breaking change

sites/svelte-5-preview/src/routes/docs/content/03-appendix/02-breaking-changes.md

@@ -222,6 +222,16 @@ This is [no longer true in Svelte 5](/#H4sIAAAAAAAAE4WQwU7DMAyGX8VESANpXe8lq9Q8A
 <svelte:component this={Thing} />
 ```
 
+### Dot notation indicates a component
+
+In Svelte 4, `<foo.bar>` would create an element with a tag name of `"foo.bar"`. In Svelte 5, `foo.bar` is treated as a component instead. This is particularly useful inside `each` blocks:
+
+```svelte
+{#each items as item}
+	<item.component {...item.props} />
+{/each}
+```
+
 ## Other breaking changes
 
 ### Stricter `@const` assignment validation