Add proxy shutdown localization (#663)

proxy/src/main/java/com/velocitypowered/proxy/VelocityServer.java

@@ -533,7 +533,7 @@ public class VelocityServer implements ProxyServer, ForwardingAudience {
    * @param explicitExit whether the user explicitly shut down the proxy
    */
   public void shutdown(boolean explicitExit) {
-    shutdown(explicitExit, Component.text("Proxy shutting down."));
+    shutdown(explicitExit, Component.translatable("velocity.kick.shutdown"));
   }
 
   @Override

proxy/src/main/resources/com/velocitypowered/proxy/l10n/messages.properties

@@ -67,3 +67,6 @@ velocity.command.dump-success=Created an anonymised report containing useful inf
 velocity.command.dump-will-expire=This link will expire in a few days.
 velocity.command.dump-server-error=An error occurred on the Velocity servers and the dump could not be completed. Please contact the Velocity staff about this problem and provide the details about this error from the Velocity console or server log.
 velocity.command.dump-offline=Likely cause: Invalid system DNS settings or no internet connection
+
+# Kick
+velocity.kick.shutdown=Proxy shutting down.