Add isProxyEnabled method to ServerConfiguration (#12664)

paper-server/src/main/java/io/papermc/paper/configuration/PaperServerConfiguration.java

@@ -1,9 +1,16 @@
 package io.papermc.paper.configuration;
 
+import org.spigotmc.SpigotConfig;
+
 public class PaperServerConfiguration implements ServerConfiguration {
 
     @Override
     public boolean isProxyOnlineMode() {
         return GlobalConfiguration.get().proxies.isProxyOnlineMode();
     }
+
+    @Override
+    public boolean isProxyEnabled() {
+        return GlobalConfiguration.get().proxies.velocity.enabled || SpigotConfig.bungee;
+    }
 }