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

bootstrap/standalone/src/main/java/org/geysermc/geyser/platform/standalone/GeyserStandaloneBootstrap.java

@@ -314,6 +314,11 @@ public class GeyserStandaloneBootstrap implements GeyserBootstrap {
         return new GeyserStandaloneDumpInfo(this);
     }
 
+    @Override
+    public @NonNull String getServerPlatform() {
+        return PlatformType.STANDALONE.platformName();
+    }
+
     @NonNull
     @Override
     public String getServerBindAddress() {