Add support for webarchives not supported by default by macOS

While macOS (and Quicklook) support web archives in .html and .webarchive formats by default, this is not the case for other common formats offered by other browsers (.mhtml, etc.) or formats from ISO norms and international standards such as .warc or .wacz.

https://en.wikipedia.org/wiki/List_of_web_archiving_file_formats