manuals: Add script to regenerate vty/counter documentation

Change-Id: I8ee63a3da532285def8de7fe5e90873152adb21e
Related: OS#1700
diff --git a/doc/manuals/Makefile.am b/doc/manuals/Makefile.am
index 52283ab..4c6b847 100644
--- a/doc/manuals/Makefile.am
+++ b/doc/manuals/Makefile.am
@@ -1,6 +1,7 @@
 EXTRA_DIST = osmosgsn-usermanual.adoc \
     osmosgsn-usermanual-docinfo.xml \
     osmosgsn-vty-reference.xml \
+    regen_doc.sh \
     chapters \
     vty