[Feature]: Twisted corner block and mirrored version

[TKOP-MECH1]

Describe the feature

Twisted corner block like this:

for clean slopes on already sloped plates example of shape being used in Avorion: (green is the shape and red is the mirrored version) vertex pattern: (O is empty X is vertex, left is base shape right is mirrored version)

top XX | XX OO | OO
bottom XO | OX XO | OX

[XFactHD]

Looks useful, I'll add it to the list of planned blocks