Update changelog with changes so far

Author: aaaaaa123456789

docs/changelog.md

@@ -2,6 +2,12 @@
 
 Note: releases are listed from latest to oldest.
 
+## Version 0.2 (in development)
+
+- Fixed a number of decoding bugs involving unusual image parameters
+- Fixed a bug with `plum_malloc` and related functions underflowing the allocation size on excessively large arguments
+- Updated the documentation to show that `data` and `palette` aliases in the `plum_image` struct exist in C11, not C99
+
 ## Version 0.1 (2 January 2022)
 
 First release.