Update copyright year in /velocity version

proxy/src/main/java/com/velocitypowered/proxy/command/VelocityCommand.java

@@ -164,7 +164,7 @@ public class VelocityCommand implements Command {
           .append(TextComponent.of(version.getVersion()).decoration(TextDecoration.BOLD, false))
           .build();
       TextComponent copyright = TextComponent
-          .of("Copyright 2018 " + version.getVendor() + ". " + version.getName()
+          .of("Copyright 2018-2019 " + version.getVendor() + ". " + version.getName()
               + " is freely licensed under the terms of the MIT License.");
       source.sendMessage(velocity);
       source.sendMessage(copyright);