fix(highlight): Whitespace color

The previous colors that Whitespace highlight group had was so obscure.
Making the view of whitespaces difficulty.
Before: https://i.imgur.com/A79qDwE.png
After: https://i.imgur.com/0CS57J0.png

lua/abyss/theme.lua

@@ -145,7 +145,7 @@ function M.get(user_opts)
     Visual = { fg = colors.none, bg = colors.darkred },
     VisualNOS = { link = "Visual" },
 
-    Whitespace = { fg = colors.bg, bg = colors.none },
+    Whitespace = { fg = colors.midblue },
 
     WildMenu = { link = "PmenuSel" },