docs(README): add save_extra_cmds quickfix example

README.md

@@ -312,12 +312,25 @@ require('auto-session').setup {
     end
   },
 
+  -- Save quickfix list and open it when restoring the session
   save_extra_cmds = {
     function()
-      return [[echo "hello world"]]
-    end
-  }
-}
+      local qflist = vim.fn.getqflist()
+      -- return nil to clear any old qflist
+      if #qflist == 0 then return nil end
+      local qfinfo = vim.fn.getqflist({ title = 1 })
+
+      for _, entry in ipairs(qflist) do
+        -- use filename instead of bufnr so it can be reloaded
+        entry.filename = vim.api.nvim_buf_get_name(entry.bufnr)
+        entry.bufnr = nil
+      end
+
+      local setqflist = 'call setqflist(' .. vim.fn.string(qflist) .. ')'
+      local setqfinfo = 'call setqflist([], "a", ' .. vim.fn.string(qfinfo) .. ')'
+      return { setqflist, setqfinfo, 'copen' }
+    end,
+  },
 ```
 
 ## ➖ Statusline