Document <prefix>.vm.threads.virtual

Author: NataliaIvakina

modules/ROOT/pages/monitoring/metrics/reference.adoc

@@ -597,6 +597,7 @@ You can limit this memory using JVM settings, but there is never any good reason
 [options="header",cols="<3m,<4"]
 |===
 |Name |Description
-|<prefix>.vm.threads|The total number of live threads including daemon and non-daemon threads. (gauge)
+|<prefix>.vm.threads|The total number of live platform threads including daemon and non-daemon threads. (gauge)
+|<prefix>.vm.threads.virtual|label:new[Introduced in 2025.05]The total number of virtual threads.
 |===