Added icons for neovim from lua

[FallenAngel97]

Hi
I really wanted to have some icons in the previewer. I'm not familiar with Vim script, so I just added https://github.com/kyazdani42/nvim-web-devicons/ through lua interface on neovim. If you have some suggestions, I can modify it

[dyng]

I have created a branch feature/add-devicon and added basic devicons (depending on [vim-devicons])(https://github.com/ryanoasis/vim-devicons).

But colored devicons need further works. You can work on my branch and this can tell you how to approach it.