Provide a Help menu that searches for all menu options

[JasonWeill]

Problem

Users might not know where a menu option is.

Proposed Solution

Provide a "Help" menu with a text box to search for commands that are present in other pull-down menus.

This could also be integrated by searching the input in the JupyterLab docs.

Additional context

macOS apps commonly have a "Help" menu which allows users to search for menu options:

On hover, the macOS UI highlights the menu item in context:

Google Docs also provides such a UI:

[JasonWeill]

Triage notes: The pull-down menus are implemented in Lumino, so this might be added (as a reduced form of the command palette) in Lumino.

[fcollonval]

Triage notes: The pull-down menus are implemented in Lumino, so this might be added (as a reduced form of the command palette) in Lumino.

I would prefer advertising and improving the command palette to address this.