DOCSP-19590 mongostat usage line (#95)

Co-authored-by: Kenneth P. J. Dyer <[email protected]>

Author: kennethdyer

source/mongostat.txt

@@ -25,11 +25,15 @@ Synopsis
 
 The :binary:`~bin.mongostat` utility provides a quick overview of the
 status of a currently running :binary:`~bin.mongod` or
-:binary:`~bin.mongos` instance. :binary:`~bin.mongostat` is functionally
+:binary:`~bin.mongos` instance.  Use :program:`mongostat` to help
+identify system bottlenecks.
+
+:binary:`~bin.mongostat` is functionally
 similar to the UNIX/Linux file system utility ``vmstat``, but provides
 data regarding :binary:`~bin.mongod` and :binary:`~bin.mongos`
 instances.
 
+
 .. include:: /includes/extracts/require-cmd-line-mongostat.rst
 
 Versioning