update changelog

Author: pchalamet

CHANGELOG.md

@@ -4,6 +4,7 @@ All notable changes to FScript are documented in this file.
 
 ## [Unreleased]
 
+- Rewrite LanguageServer to C#.
 - Enabled F# preview parallel compilation globally, disabled deterministic builds, and removed global RuntimeIdentifiers to reduce CI build latency.
 - Added `FScript.CSharpInterop` as a stable bridge for parse/infer/runtime-extern/stdlib-source services and wired LanguageServer through it.
 - Added `FScript.LanguageServer` host executable as the migration entrypoint for C#-owned LSP startup.