Inherit theme fg and bg from given highlighting group

[mitinarseny]

I like feline for a lot of reasons, but when it comes to write colors in hex, it frustrates me.

I use https://github.com/arcticicestudio/nord-vim colorcheme, so when call :colorscheme nord all the colors are set from its colors/ and they are not exposed to user except for global function NordPalette() which I don't want to depend on for a number of reasons.

It would be nice if feline could inherit guibg and guifg from given highlighting groups for all components, which do not explicitly provide hl:

require('feline').setup({
  theme = {
    bg = 'StatusLineNC',
    fg = 'Normal',
  },
})

[vladimir-popov]

it was suggested previously #167

[famiu]

Yeah, I have no intention of implementing this. Just use nvim_get_hl_by_name