policer: adding documentation

Type: docs

Several kinds of policers are implemented in VPP.
However, they could differ from the RFCs it is
said they are from.

Additionally, the CLI command's help has been
updated with the current list of acceptable
parameters.

Signed-off-by: Maxime Peim <mpeim@cisco.com>
Change-Id: Ic9bf94e1094bea0fcc87ccaa882c2c5f88824041
diff --git a/docs/developer/corefeatures/index.rst b/docs/developer/corefeatures/index.rst
index 1012387..8daadaa 100644
--- a/docs/developer/corefeatures/index.rst
+++ b/docs/developer/corefeatures/index.rst
@@ -20,3 +20,4 @@
     eventviewer
     stats
     selinux_doc
+    policer