Cant't change the name of main html file in the output of `nim doc`?

[PMunch]

I believe this is because if you had two modules in your project it's nice that 
they're named after the module they come from and not one simply being called 
`index.html`. Manually moving it (or just moving it from the same script that 
runs nim), or even just having a symlink from `index.html` to `foo.html` is 
probably the best solution.