[Feature]: Double Half slope (probably a different name)

[gameralike]

Describe the feature

While creating pathways, i realized i needed a block that can smooth the transition from sloped blocks to double slabs. I thought this might be a good addition if not already planned.

[XFactHD]

The part of the block marked with 1 in your drawing already exists, so this is a fitting extension on top of that. I'll add it to the planned blocks.