Check downloaded filings and parsed items

[hahoangnhan]

Hi,
Thanks for sharing a great package.
It's not a real issue, but I hope you can update to check if a filing has been downloaded and an item has been parsed in the next version. And by that, we need to download missing filings and parse missing items as needed.

Sometimes the computer could get crashed and let me restart my session. I saw some filings and items in the output folders, but restarting the session requires Python to start from the beginning. Checking downloaded filings is also helpful in case we want to update the data.

Best regards,
hhn