A "card_size" config option for history-graph cards

[JamoDevNich]

This is a suggestion for a 'card_size' option on history-graph cards, to allow the UI to arrange these cards optimally in the interface. At present, the markdown card offers such an option.

The initial history-graph card state is compact and completely visible in the browser viewport

After loading completes, some cards are pushed outside of the browser viewport

Sidenote: the cards are not inside a -stack, they are at the topmost level of this page's 'cards' key