Add doc modification script
Add doc modification script

This is a script to modify the docs in some fashion. Right now it just
adds an image to the header, but it will replace a couple of other
things, in a nicer fashion.

Roughsketch/serenity,Flat/serenity,zeyla/serenity.rs,acdenisSK/serenity,zeyla/serenity,Lakelezz/serenity,eLunate/serenity