There's https://warcreate.com/, but it's for Chrome. I don't know details of it, but aren't both browsers use the same API for extensions? Then probably it's possible to port it, or to install right away.

It creates .warc files, which are supported by Internet Archive. I don't know if it integrates uploaded .warc files to Wayback Machine, but Archive Team uses this format to upload manually archived sites to Internet Archive.