Ability to use custom font families

[Nagidrop]

Is your feature request related to a problem? Please describe.

Currently I cannot use other font families aside from the extension's listed fonts.

Describe the solution you'd like

It would be nice to allow adding custom fonts directly into the font family combo box. Alternatively, simply adding a text box for users to type in their desired fonts (similar to the built-in JupyterLab Desktop's Theme settings) is also great.

Describe alternatives you've considered

I tried using custom fonts in the JupyterLab Desktop's Theme settings in conjunction with the extension's custom colors, but they don't work simultaneously. Besides, I cannot find any other easy solutions to change UI colors.

Additional context

The ability to easily and freely use customised fonts will not only help novice users like me, but also save advanced users a lot of time.

• Python package version: 0.4.2

• Extension version: 0.4.2

• Operating System and its version: Windows 11 22H2