Add v0.23.1 to changelog (eclipse-lsp4j#839)

Part of eclipse-lsp4j#838

Author: jonahgraham

CHANGELOG.md

@@ -8,6 +8,13 @@ Breaking API changes:
 
 japicmp report: <https://download.eclipse.org/lsp4j/builds/main/japicmp-report/>
 
+### [v0.23.1 (May 2024)](https://github.com/eclipse-lsp4j/lsp4j/releases/tag/v0.23.1)
+
+Fixed issues: <https://github.com/eclipse-lsp4j/lsp4j/milestone/36?closed=1>
+
+Breaking API changes:
+
+japicmp report: <https://download.eclipse.org/lsp4j/updates/releases/0.23.1/japicmp-report/>
 
 ### [v0.23.0 (May 2024)](https://github.com/eclipse-lsp4j/lsp4j/releases/tag/v0.23.0)