Slight changes to local build instructions

[lnmiltz]

Hi,

I've been trying to build this on my machine and test out some changes. I ran into a lot of problems with yarn, but managed to get it working in the end.

I tried yarn serve docs, but this brought up a blank page (not completely blank but the .html file was confusing and short). I messed around with it and had to make two changes to get it to work:

1. Change
   
   to
   

2. Use yarn serve build instead of yarn serve docs

I haven't done much with node or yarn so I don't know why this works. Maybe this is only necessary for hosting locally, but a note about this in the readme would be helpful for anyone else who gets stuck.

I'm glad I did get it working though, the overlay looks great and now I can keep customizing it!

[bsides]

Hi @lnmiltz,

We may need a better investigation, but a PR is always welcome!

Thank you