Set status line theme to the global colorscheme

instead of hardcoding the 'onedark' theme.
It allows users to change the Neovim theme globally and to see those
changes automatically reflected to the status line.

init.lua

@@ -205,7 +205,7 @@ require('lazy').setup({
     opts = {
       options = {
         icons_enabled = false,
-        theme = 'onedark',
+        theme = 'auto',
         component_separators = '|',
         section_separators = '',
       },