Proposal: Ensure the Menu items show the keyboard shortcuts
Guidance: Keyboard accelerators

(note: yes the CTRL+Down is incorrect for settings, working on fixing that)

When enabling keyboard users, helping them not have to hunt for productive shortcuts is a good user experience. When using menus, it is best practice if a shortcut exists, to surface that to the user like above.

Changes are simple since the keyboard shortcuts are already there, changes to TerminalApp\App.cpp are all that are needed.

Questions:
[] How would this affect custom keybindings in #537 ?