dock: Add menu item to open projector

[norihiro]

Description

As the activities of #86, the key was added. However, the labels are too small when the dock was small.

To easily see the key and it's labels, add a menu item that opens a projector window of the right-clicked scope.

How Has This Been Tested?

Tested on Fedora 39.

General checklist

• [x] The commit is reviewed by yourself.
• [x] The code is tested.
• [x] Document is up to date or not necessary to be changed.
• [x] The commit is compatible with repository's license.