Update changelog for #2625 and #2621 (#2636)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2994ce5..699545a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md

@@ -78,6 +78,10 @@
   avifRGBImageAllocatePixels().
 * Make avifEncoder.headerFormat a flag combination for future features.
 * Rename AVIF_HEADER_FULL to AVIF_HEADER_DEFAULT. Deprecate AVIF_HEADER_FULL.
+* Fix decoding image sequences with non video tracks (such as audio or subtitles).
+* Fix type checking of auxiliary tracks: previously any auxiliary track was
+  assumed to be alpha, even if it was a different type. If the aux type is absent,
+  it is assumed to be alpha.
 
 ## [1.1.1] - 2024-07-30