High contrast option

[asdil12]

The original zenburn comes with an option for high contrast.
Could this be introduced here as well?

" CONFIGURABLE PARAMETERS:
"
" You can use the default (don't set any parameters), or you can
" set some parameters to tweak the Zenburn colours.
"
" To use them, put them into your .vimrc file before loading the color scheme,
" example:
"    let g:zenburn_high_Contrast=1
"    colors zenburn
"
" You can also do ":let g:zenburn" then hit Ctrl-d or Tab to scroll through the
" list of configurable parameters.
"
" * You can now set a darker background for bright environments. To activate, use:
"      let g:zenburn_high_Contrast = 1
"

[asdil12]

I created a fork that uses the right colors for the high contrast mode:
https://github.com/asdil12/zenburn.nvim

This is how it looks like:

Maybe we could include this in zenburn.nvim with some configuration to select the color mode?