Update CHANGELOG for v1.5.15

***NO_CI***

Author: nfbot

CHANGELOG.md

@@ -2,7 +2,15 @@
 
 ## [**Changes available only in 'Preview' NuGet packages:**](https://github.com/nanoframework/System.Math/tree/HEAD)
 
-[Full Changelog](https://github.com/nanoframework/System.Math/compare/v1.5.10...HEAD)
+[Full Changelog](https://github.com/nanoframework/System.Math/compare/v1.5.12...HEAD)
+
+**Documentation and other chores:**
+
+- Update 5 NuGet dependencies [\#125](https://github.com/nanoframework/System.Math/pull/125)
+
+## [v1.5.12](https://github.com/nanoframework/System.Math/tree/v1.5.12) (2022-10-24)
+
+[Full Changelog](https://github.com/nanoframework/System.Math/compare/v1.5.10...v1.5.12)
 
 **Documentation and other chores:**