doc: Add generic counter chapter in manual

Depends: I01b8529136450cb50e48b0fb5c17cb2daa5e24c3 (osmo-gsm-manuals)
Change-Id: Ida53d79787aedc5b37a68e6795a863cb0b4a343a
diff --git a/doc/manuals/chapters/counters.adoc b/doc/manuals/chapters/counters.adoc
index 7fbb10c..be92369 100644
--- a/doc/manuals/chapters/counters.adoc
+++ b/doc/manuals/chapters/counters.adoc
@@ -1,4 +1,4 @@
 [[counters]]
-== Counters
+== Implemented Counters
 
 include::./counters_generated.adoc[]