CI: add note about running scripts locally

.build.yml

@@ -2,6 +2,8 @@ image: alpine/edge
 packages:
   - sudo
 tasks:
+  - note: |
+      pmbootstrap/.ci/note.sh
   - shellcheck: |
       cd pmbootstrap
       sudo .ci/shellcheck.sh

.ci/note.sh

@@ -0,0 +1,6 @@
+#!/bin/sh -e
+
+printf "\n"
+printf "PROTIP: use"
+printf " \e[1;32mpmbootstrap ci\e[0m"
+printf " to run these scripts locally.\n"