Add option to set default view via settings

For https://landscape.nixlang.wiki we wanted to use the card view instead of the grid view as the default. Sadly, we currently have to compile our own version of landscap2 just to change this.

We would love if there was an option for this instead!

This part of the code might be relavant:

landscape2/web/src/data.ts

Line 46 in 4365ca1

export const DEFAULT_VIEW_MODE = ViewMode.Grid;

Thanks @cafkafk, we'll make this configurable 🙂

Done!

Closed by #572 and #574