CMP: Change default neovim snippet engine to luasnip for expanding completions

lua/custom/completion.lua

@@ -49,7 +49,7 @@ cmp.setup {
   -- Enable luasnip to handle snippet expansion for nvim-cmp
   snippet = {
     expand = function(args)
-      vim.snippet.expand(args.body)
+      require("luasnip").lsp_expand(args.body)
     end,
   },