README_accelergy.md and README_layout.md are missing

[singyaowu]

Hi, thank you for the great work on SCALE-Sim!

I noticed that README.md references README_accelergy.md and README_layout.md for the Accelergy and Layout features, but I wasn't able to find either of those files in the repository. It's a bit hard to get started with those features without the documentation.

Would it be possible to add those files, or point to wherever the documentation lives?

Thanks!