Feature request: Add option to pack all assets into the html files directly

[MuffinOfPotato]

I'm really glad that there's an option to store images and other relevant assets locally, but it's all stored into separate folders. One can already achieve this manually with SingleFile, but to help ease tasks like the transferring/sharing of chat archives without needing to package supplementary file folders, I think it would be very convenient to have an option that automatically stores all downloaded assets into the html files themselves.