Add missing changelog for `avifdec --index all` (#2672)

Fix int => avifBool.

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 806aeb5..8faff2c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,12 @@
 
 ## [Unreleased]
 
+### Added since 1.2.0
+
+* Add support for outputting all frames of an image sequence in `avifdec`. 
+  `avifdec --index all sequence.avif out.png` creates files named
+  `out-xxxxxxxxxx.png` where xxxxxxxxxx are the zero-padded frame indices.
+
 ### Changed since 1.2.0
 
 * Fix local libargparse dependency patch step on macOS 10.15 and earlier.

apps/avifdec.c

diff --git a/apps/avifdec.c b/apps/avifdec.c
index bc4f6cf..f30a90c 100644
--- a/apps/avifdec.c
+++ b/apps/avifdec.c
@@ -330,7 +330,7 @@
     printf("Image decoded: %s\n", inputFilename);
     avifContainerDump(decoder);
 
-    const int isSequence = decoder->imageCount > 1;
+    const avifBool isSequence = decoder->imageCount > 1;
     printf(" * %" PRIu64 " timescales per second, %2.2f seconds (%" PRIu64 " timescales), %d frame%s\n",
            decoder->timescale,
            decoder->duration,