Add script that describes how to build Debian package

Users have expressed a [desire for Debian packaging][#125 (closed)] of LibreWolf. Using the output of the script included in this pull request, I have deployed LibreWolf 83.0-1 to the Open Build Service for Debian Sid. The script in this request is annotated, and can be run to build the assets required to run your own dpkg-buildpackage to get a LibreWolf dpkg! It is possible that these contents belong as a "Debian" project underneath https://gitlab.com/librewolf-community/browser if somebody here would like to maintain this going forward. It is worth noting that this script operates by modifying the Debian Firefox source package, which operates a little differently than the binary release of LibreWolf. Two changes worth noting: Debian uses gcc to compile Firefox/LibreWolf and not clang. Debian disables the crashreporter functionality at compile time.