fix(base16): don't set background where not neeeded

Details:
- `ErrorMsg` having background doesn't work if it is displayed in not
  usual "message area" (like in floating window of `vim._extui` on
  Neovim>=0.12).
- `MsgArea` doesn't need background to be the same as `Normal` bg.
- `PmenuMatch[Sel]` groups don't need background as they will blend with
  `Pmenu`.
- `PmenuKind[Sel]` and `PmenuExtra[Sel]` also don't need background, but
  only on Neovim>=0.11. So instead link them to corresponding `Pmenu`
  (which is more appropriate solution for them anyway).

Author: echasnovski

lua/mini/base16.lua

@@ -485,7 +485,7 @@ H.apply_palette = function(palette, use_cterm)
   hi('DiffTextAdd',    {link='DiffAdd'})
   hi('Directory',      {fg=p.base0D, bg=nil,      attr=nil,            sp=nil})
   hi('EndOfBuffer',    {fg=p.base03, bg=nil,      attr=nil,            sp=nil})
-  hi('ErrorMsg',       {fg=p.base08, bg=p.base00, attr=nil,            sp=nil})
+  hi('ErrorMsg',       {fg=p.base08, bg=nil,      attr=nil,            sp=nil})
   hi('FloatBorder',    {link='NormalFloat'})
   hi('FoldColumn',     {fg=p.base0C, bg=p.base01, attr=nil,            sp=nil})
   hi('Folded',         {fg=p.base03, bg=p.base01, attr=nil,            sp=nil})
@@ -499,20 +499,20 @@ H.apply_palette = function(palette, use_cterm)
   hi('MatchParen',     {fg=nil,      bg=p.base02, attr=nil,            sp=nil})
   hi('ModeMsg',        {fg=p.base0B, bg=nil,      attr=nil,            sp=nil})
   hi('MoreMsg',        {fg=p.base0B, bg=nil,      attr=nil,            sp=nil})
-  hi('MsgArea',        {fg=p.base05, bg=p.base00, attr=nil,            sp=nil})
+  hi('MsgArea',        {fg=p.base05, bg=nil,      attr=nil,            sp=nil})
   hi('MsgSeparator',   {fg=p.base02, bg=p.base02, attr=nil,            sp=nil})
   hi('NonText',        {fg=p.base03, bg=nil,      attr=nil,            sp=nil})
   hi('Normal',         {fg=p.base05, bg=p.base00, attr=nil,            sp=nil})
   hi('NormalFloat',    {fg=p.base05, bg=p.base01, attr=nil,            sp=nil})
   hi('NormalNC',       {fg=p.base05, bg=p.base00, attr=nil,            sp=nil})
   hi('OkMsg',          {fg=p.base0B, bg=nil,      attr=nil,            sp=nil})
   hi('Pmenu',          {fg=p.base05, bg=p.base01, attr=nil,            sp=nil})
-  hi('PmenuExtra',     {fg=p.base05, bg=p.base01, attr=nil,            sp=nil})
-  hi('PmenuExtraSel',  {fg=p.base05, bg=p.base01, attr='reverse',      sp=nil})
-  hi('PmenuKind',      {fg=p.base05, bg=p.base01, attr=nil,            sp=nil})
-  hi('PmenuKindSel',   {fg=p.base05, bg=p.base01, attr='reverse',      sp=nil})
-  hi('PmenuMatch',     {fg=p.base05, bg=p.base01, attr='bold',         sp=nil})
-  hi('PmenuMatchSel',  {fg=p.base05, bg=p.base01, attr='bold,reverse', sp=nil})
+  hi('PmenuExtra',     {link='Pmenu'})
+  hi('PmenuExtraSel',  {link='PmenuSel'})
+  hi('PmenuKind',      {link='Pmenu'})
+  hi('PmenuKindSel',   {link='PmenuSel'})
+  hi('PmenuMatch',     {fg=p.base05, bg=nil,      attr='bold',         sp=nil})
+  hi('PmenuMatchSel',  {fg=p.base05, bg=nil,      attr='bold,reverse', sp=nil})
   hi('PmenuSbar',      {fg=nil,      bg=p.base02, attr=nil,            sp=nil})
   hi('PmenuSel',       {fg=p.base05, bg=p.base01, attr='reverse',      sp=nil})
   hi('PmenuThumb',     {fg=nil,      bg=p.base07, attr=nil,            sp=nil})