Fix #158 [nvim-cmp] documentation is deprecated

lua/user/cmp.lua

@@ -117,8 +117,10 @@ cmp.setup {
     behavior = cmp.ConfirmBehavior.Replace,
     select = false,
   },
-  documentation = {
+  window = {
-    border = { "╭", "─", "╮", "│", "╯", "─", "╰", "│" },
+    documentation = {
+      border = { "╭", "─", "╮", "│", "╯", "─", "╰", "│" },
+    },
   },
   experimental = {
     ghost_text = false,