Add changelog

Author: plemarquand

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - Fix the wrong toolchain being shown as selected when using swiftly v1.0.1 ([#2014](https://github.com/swiftlang/vscode-swift/pull/2014))
 - Fix extension displaying SwiftPM's project view and automatic build tasks even when `disableSwiftPMIntegration` was true ([#2011](https://github.com/swiftlang/vscode-swift/pull/2011))
+- Validate extension settings and warn if they are invalid ([#2016](https://github.com/swiftlang/vscode-swift/pull/2016))
 
 ## 2.14.3 - 2025-12-15