Update CHANGELOG.md

Author: tanhauhau

CHANGELOG.md

@@ -7,6 +7,7 @@
 * Add a11y warning `a11y-no-abstract-role` which checks ARIA roles must be non-abstract ARIA role ([#6241](https://github.com/sveltejs/svelte/pull/6241))
 * Add a11y warning `a11y-no-interactive-element-to-noninteractive-role` which checks for noninteractive roles used on interactive elements ([#5955](https://github.com/sveltejs/svelte/pull/5955))
 * Remove of empty stylesheets created from transitions ([#4801](https://github.com/sveltejs/svelte/issues/4801), [#7164](https://github.com/sveltejs/svelte/issues/7164))
+* Disallow invalid CSS selectors starting with a combinator ([#7643](https://github.com/sveltejs/svelte/issues/7643))
 
 ## 3.49.0