Allow for manually starting workflow to build devel images (#14955)

.github/workflows/devel_images.yml

@@ -3,6 +3,7 @@ name: Build/Push Development Images
 env:
   LC_ALL: "C.UTF-8" # prevent ERROR: Ansible could not initialize the preferred locale: unsupported locale setting
 on:
+  workflow_dispatch:
   push:
     branches:
       - devel