[REQ] Support for .sitebuilder archive

[sulliops]

Describe the solution you'd like

I have a file (attached in zipped form because GitHub) that is of a proprietary archive format (.sitebuilder), but functions like a .7z archive. The 7z command-line utility can extract it without any extra configuration, but I've yet to find a GUI extractor that can handle it. It's super niche, but I work with these files from time to time and it'd be nice to have a way to handle them quickly on macOS.

File (zipped): test.sitebuilder.zip

Additional context

There is no publicly-available documentation for this file format, but 7z reports the file structure as a zip with an offset of 43.

[aonez]

It has the signature SProBuilder99ac8c93403168fe18999b9b3d67902fPK so it's really based on ZIP (PK at the end) but the structure is slightly different. That's why the 43 offset, the extra SProBuilder99ac8c93403168fe18999b9b3d67902f at the signature.

Can you provide more examples?

[sulliops]

Attached is a zip of five more .sitebuilder archives of various sizes that appear to match the same general structure as the first one I linked. I think it's reasonable to assume that the structure is standardized for these files.

more_files.zip