add top bedrock depth

[mantonovic]

Optional, but If defined, style the upper border.

[mantonovic]

Adding a bedrock boolean variable at the layer:

    ... {
            id: 2,
            bedrock, // <<<<
            from: 1.23,
            to: 1.77,
            color: '#789123',
            pattern: 'assets/pattern-2.png',
            title: 'Quartar, undifferenziert',
            subtitle: 'Phonolith'
     } ...