Support shouldLanguageServerExitOnShutdown capability

Supports the capability, which means that language server shuts down
when `shutdown` is received instead of when `exit` is received.

See eclipse-lemminx/lemminx#1070

Signed-off-by: David Thompson <davthomp@redhat.com>

Author: datho7561

CHANGELOG.md

@@ -24,6 +24,7 @@
  * CodeLens does not work in binary. See [eclipse/lemminx#1046](https://github.com/eclipse/lemminx/issues/1046).
  * Error while saving file to cache on Windows OS (PosixFileAttributeView not supported). See [eclipse/lemminx#734](https://github.com/eclipse/lemminx/issues/734).
  * Extension doesn't start when running in vscode < 1.55. See [#520](https://github.com/redhat-developer/vscode-xml/pull/520).
+ * Language server remains running after VS Code stops. See [#TODO](https://github.com/redhat-developer/vscode-xml/pull/TODO).
 
 ## [0.16.1](https://github.com/redhat-developer/vscode-xml/milestone/20?closed=1) (May 18, 2021)
 

src/client/xmlClient.ts

@@ -129,7 +129,8 @@ function getLanguageClientOptions(logfile: string, externalXmlSettings: External
           }
         },
         actionableNotificationSupport: true,
-        openSettingsCommandSupport: true
+        openSettingsCommandSupport: true,
+        shouldLanguageServerExitOnShutdown: true
       }
     },
     errorHandler: new ClientErrorHandler('XML'),