This software is by no means stable and you shouldn't depend on it unless you're comfortable with editing the source yourself.
You will need to install zig.
Depends on zig-date as a submodule.
git clone --recurse-submodules https://github.com/clarityflowers/sitegen.git cd sitegen zig build
This will produce
zig-cache/bin/sitegen. To install to, say,
~/bin, you could instead run
zig-cache --prefix ~.
All of the code is inside src/main.zig. At the top of the file is a doc comment with some directions on where to find what you're looking for.