Add some more high-level settings configuration actions

[bollwyvl]

Elevator Pitch

Allow more of the jyg configuration options to be modified through menus, commands, etc.

Motivation

At present, jyg basically works in the Retrolab-based Jupyterlite app, but boards can't be opened unles pre-configured (or configured in /lab and switching back).

Design Ideas

Add Main Menu/Command Palette for:

• Open Command Boards In [popup|[main|...]area]
• ???