Add scrolloff option for completion window.

lua/cmp/config/default.lua

@@ -91,6 +91,7 @@ return function()
       completion = {
         border = { '', '', '', '', '', '', '', '' },
         winhighlight = 'Normal:Pmenu,FloatBorder:Pmenu,CursorLine:PmenuSel,Search:None',
+        scrolloff = 0,
         col_offset = 0,
         side_padding = 1,
       },

lua/cmp/config/window.lua

@@ -6,6 +6,7 @@ window.bordered = function(opts)
     border = opts.border or 'rounded',
     winhighlight = opts.winhighlight or 'Normal:Normal,FloatBorder:Normal,CursorLine:Visual,Search:None',
     zindex = opts.zindex or 1001,
+    scrolloff = opts.scrolloff or 0,
     col_offset = opts.col_offset or 0,
     side_padding = opts.side_padding or 1,
   }