add vlsiffra notebook

[proppy]

Upstream:
https://github.com/antonblanchard/vlsiffra

Hard-Dependencies:
yosys (but can use https://github.com/amaranth-lang/amaranth-yosys)

Soft-Dependencies:

• OpenROAD
• ORFS
• open_pdks.{sky130a,gf180mcuc)

Usage:

• as a tool: https://github.com/antonblanchard/vlsiffra#example-usage
• as an amaranth Elaborate: https://github.com/antonblanchard/vlsiffra/blob/main/vlsiffra/adder.py#L6

[proppy]

Also potentially explore packaging it natively with conda-eda: hdl/conda-eda#248