Ice40 placement#590

Draft

tcal-x wants to merge 3 commits intogoogle:mainfrom

tcal-x:ice40-placement

Commits on May 14, 2022

Scripts for plotting ice40 placement.
Tim Callahan
committed

Commits on May 20, 2022

Update ice40 plotting scripts & invoke from ice40 flow.
Tim Callahan
committed
Add matplotlib to Python requirements.txt.
Tim Callahan
committed