design: Add "design" topic to gerrit reviews

This allows a query like this to be run to find all open design docs:
https://gerrit.openbmc-project.xyz/#/q/topic:design+status:open

This allows easy searching for design reviews in gerrit.

Change-Id: Ia9dbdf0b762af7713e2cbd647ca45a8c5a609424
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/designs/design-template.md b/designs/design-template.md
index 892e01e..20f194b 100644
--- a/designs/design-template.md
+++ b/designs/design-template.md
@@ -21,6 +21,8 @@
   ASCII diagrams.  Plain text will allow the review to proceed without
   having to look at additional files which can not be viewed in Gerrit.  It
   will also allow inline feedback on the diagram itself.
+* Once ready for review, submit to gerrit and set the topic of the review
+  to "design"
 ____
 
 # Example design - this is the design title