feat: Start a single frame with a pre-selected default node shape

When initiating a single frame with Roger, the user currently needs to choose a node shape from the menu. It is necessary to include a feature where Roger is initiated with a default node shape already selected.

How?

Add property data with type Quad[] to function SingleFrame. In your app, hand down the quad with the predicate rdf:type to the SingleFrame component.

The resolution of this issue depends on #9 and is thus blocked by #9.