Added a new entry for Automate Explorer in miq_shortcuts.yml

This will add Automate Explorer as a startup page.

https://bugzilla.redhat.com/show_bug.cgi?id=1129113
Merge pull request #622 from AparnaKarve/bz1129113_add_automate_explorer_page_as_startup

Added a new entry for Automate Explorer in miq_shortcuts.yml