Get Discord Attachment URLs wót Ydloader

This is a drop-dead simple add-on.
Usage:
1. Only enable this add-on when you need to use it.
2. Navigate to a channel in Discord that contains attachments.
3. A button should appear in the lower right to "Export ALL". Click it and let it grab the URLs
4. URLs will be copied to clipboard. That's it!

Copied URLs can be saved to a text file, imported into download managers like DownThemAll, etc.