Add lobby/game worlds, void generator, dbd reload, and fix plugin loading

- Add VoidWorldGenerator for empty void worlds
- Add LobbyManager with auto-creation of lobby world (stone platform 7x7, built once) and game world
- Add /dbd reload command to reload all configs at runtime
- Add plugin.yml for proper command registration, remove paper-plugin.yml
- Fix mdbdBootstrap/mdbdLoader public constructors (Paper requirement)
- Fix command registration (getCommand null on Paper plugin system)

src/main/java/dev/loki/mdbdBootstrap.java

@@ -3,7 +3,9 @@ package dev.loki;
 import io.papermc.paper.plugin.bootstrap.BootstrapContext;
 import io.papermc.paper.plugin.bootstrap.PluginBootstrap;
 
-class mdbdBootstrap implements PluginBootstrap {
+public class mdbdBootstrap implements PluginBootstrap {
+
+    public mdbdBootstrap() {}
 
     @Override
     public void bootstrap(final BootstrapContext context) {