docs: add info about new metrics to README.rst

Author: casperr0

README.rst

@@ -346,6 +346,19 @@ Metrics:  PostgreSQL
     'PostgreSQL waits: Other operations': pgsql.lwlock[other]
     'PostgreSQL: number of prepared transactions': 'pgsql.prepared.count'
     'PostgreSQL: oldest prepared transaction running time in sec': 'pgsql.prepared.oldest'
+    'PostgreSQL: number of PostgreSQL parent pid children': pgsql.count_all_pids[]
+    'PostgreSQL: number of pids which private anonymous memory exceeds private_anon_mem_threshold':
+    pgsql.memory_leak_diagnostic.count_diff[]
+    'PostgreSQL: number of pids which private anonymous memory exceeds exceeds private_anon_mem_threshold,
+    text of message': pgsql.memory_leak_diagnostic.msg_text[]
+    'PostgreSQL: time elapsed between flushing recent WAL locally and receiving notification that this standby server
+    has written and flushed it': pgsql.replication.flush_lag
+    'PostgreSQL: time elapsed between flushing recent WAL locally and receiving notification that this standby server
+    has written, flushed and applied': pgsql.replication.replay_lag
+    'PostgreSQL: time elapsed between flushing recent WAL locally and receiving notification that this standby server
+    has written it': pgsql.replication.write_lag
+    'PostgreSQL: delta of total lag for {#APPLICATION_NAME}': pgsql.replication.total_lag
+    'PostgreSQL: count non-active replication slots': pgsql.replication.non_active_slots
 
     'Pg_probackup catalog {#BACKUPDIR}: size':  pg_probackup.dir.size[{#BACKUPDIR}]
     'Pg_probackup catalog {#BACKUPDIR}: error': 'pg_probackup.dir.error[{#BACKUPDIR}]