docs: override colors inside vim config example (#104)

README.md

@@ -145,6 +145,12 @@ let g:tokyonight_style = "night"
 let g:tokyonight_italic_functions = 1
 let g:tokyonight_sidebars = [ "qf", "vista_kind", "terminal", "packer" ]
 
+" Change the "hint" color to the "orange" color, and make the "error" color bright red
+let g:tokyonight_colors = {
+  \ 'hint': 'orange',
+  \ 'error': '#ff0000'
+\ }
+
 " Load the colorscheme
 colorscheme tokyonight
 ```