HackStudio: Integate with C++ parser-based autocomplete

By default, C++ auto completion will still be performed by the
lexer-based logic.
However, the parser-based logic can be switched on via the menubar.

Userland/DevTools/HackStudio/LanguageClient.cpp

@@ -25,6 +25,7 @@
  */
 
 #include "LanguageClient.h"
+#include "DevTools/HackStudio/LanguageServers/LanguageServerEndpoint.h"
 #include <AK/String.h>
 #include <AK/Vector.h>
 
@@ -72,4 +73,9 @@ void LanguageClient::provide_autocomplete_suggestions(const Vector<GUI::Autocomp
     // Otherwise, drop it on the floor :shrug:
 }
 
+void LanguageClient::set_autocomplete_mode(const String& mode)
+{
+    m_connection.post_message(Messages::LanguageServer::SetAutoCompleteMode(mode));
+}
+
 }