changelog: add some final 0.26 changes

Author: ethomson

CHANGELOG.md

@@ -24,12 +24,17 @@ v0.25 + 1
 * We now optionally call `fsync` on loose objects, packfiles and their indexes,
   loose references and packed reference files.
 
-* We can now build against OpenSSL v1.1.
+* We can now build against OpenSSL v1.1 and against LibreSSL.
 
 * `GIT_MERGE_OPTIONS_INIT` now includes a setting to perform rename detection.
   This aligns this structure with the default by `git_merge` and
   `git_merge_trees` when `NULL` was provided for the options.
 
+* Improvements for reading index v4 files.
+
+* Perform additional retries for filesystem operations on Windows when files
+  are temporarily locked by other processes.
+
 ### API additions
 
 * New family of functions to handle worktrees: