Add change log for a potential, not-yet-released 0.15.1

Author: Ericson2314

ChangeLog.md

@@ -1,5 +1,15 @@
 ## Release History
 
+## 0.15.1 (not yet released)
+
+The objective is to prepare a very conservative patch release which can be bumped in Nixpkgs immediately.
+
+* Backport infra changes from later master (August 2025)
+* Backport shellcheck fixes to test suite
+* Backport C++ code quality fixes (all of https://github.com/NixOS/patchelf/pull/464 but the final two commits)
+
+The behavior of this version should be essentially the same as 0.15.0.
+
 ## 0.15.0 (Jul 16, 2022)
 
 * Add --add-debug option by @deadw00d in https://github.com/NixOS/patchelf/pull/367