Indicate 1.21.112/1.21.113 support, track server platform types in bstats metrics

bootstrap/viaproxy/src/main/java/org/geysermc/geyser/platform/viaproxy/GeyserViaProxyPlugin.java

@@ -230,6 +230,11 @@ public class GeyserViaProxyPlugin extends ViaProxyPlugin implements GeyserBootst
         return new GeyserViaProxyDumpInfo();
     }
 
+    @Override
+    public @NonNull String getServerPlatform() {
+        return PlatformType.VIAPROXY.platformName();
+    }
+
     @NonNull
     @Override
     public String getServerBindAddress() {