Description of the new feature/enhancement

Currently, bringing up the new tab drop down requires using arrow keys to move to each option. It would make accessibility easier if users could press access keys that correlate with each entry to jump to that entry or cycle through similarly identified entries.

Proposed technical implementation details (optional)

One possible solution: If the menu looks like the following,

• PowerShell
• Command Prompt
• PSCore
• Settings
• Feedback
• About

It would be helpful if a user could press p twice to select "PSCore" or c once to select "Command Prompt". This may be doable simply by setting AccessKey for each MenuFlyoutItem in TerminalPage::_CreateNewTabFlyout.

Another possible solution would be to support _ syntax, mirroring WPF's implementation in the config JSON's profile names.