Feature request for dimming inactive windows?

What are your thoughts on extending limelight to dim inactive windows? I'm able to get close with plugins like [vim-diminactive](https://github.com/blueyed/vim-diminactive) and [vim-high](https://github.com/bimlas/vim-high), but not able to dim everything. Example...


For example, those plugins are unable to dim vim-gitgutter signs, or my green `CursorLineNR` highlighting there. I love your goyo and limelight plugin implementations, they are very customizable! What are your thoughts on adding this inactive window dimming functionality to limelight?

PS. It seems @duckwork has done some awesome work getting this started [in his fork of limelight](https://github.com/duckwork/limelight.vim/commits/master) with [an example here](https://www.reddit.com/r/neovim/comments/4dyaqt/how_i_can_dim_inactive_windows/d1vgs25/) 👌 Though like the above mentioned window dimming plugins, I still can't dim gutter/sign related highlights.

Start by reviewing the limelight.vim implementation and the linked duckwork/limelight.vim fork commits, then compare the referenced dimming plugins and example. Done means inactive windows are dimmed consistently, including gutter and sign-related highlights, while active-window highlighting remains usable.

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