docs: how to add an upgrade layer

packages/deployment/upgrade-test/Readme.md

@@ -102,6 +102,17 @@ docker exec -it sweet_edison bash
 To make the wallet ui talk to your local chain, set the network config to
 `https://local.agoric.net/network-config`
 
+## To add an upgrade
+
+1. Update the upgrade handler in app.go
+2. Duplicate the last pair of UPGRADE and TEST blocks
+3. Update their number from the UPGRADE / DEST block at the end
+4. Update the UPGRADE/DEST pair to be your new upgrade (THIS_NAME matching the upgrade handler string in app.go)
+5. Add the two targets to `Makefile` (e.g. `agoric-upgrade-11-to-12` and `agoric-upgrade-12`)
+6. Add the DEST target to the `.phony` in `Makefile`
+5. Test with `make local_sdk build run`
+
+
 ## Development
 
 You can iterate on a particular upgrade by targeting. When you exit and run again, it will be a fresh state.