Add Package installer for Slackware Please

Slackware uses no dependency checking, and 4 bash scripts form the package tools. The packages are basically tar xz archives abbreviated to txz.

1. Installpkg - as it says.
2. Removepkg - as it says
3. Upgradepkg - will upgrade or downgrade a package
4. Makepkg - will make a package
5. explodepkg will open a package in the current directory

Slackware has a pkgtools package which can be exploded (tar -xvf) and examined. To make a package, run a few commands

There's no dependencies to be searched down. We do that ourselves.

Start by examining the existing install.sh entry points and Slackware's pkgtools, using the linked Slackbook package-management reference for context. Determine how the installer should invoke installpkg, removepkg, upgradepkg, makepkg, and explodepkg; done means Slackware packages are handled without dependency resolution.

Written by the indexing model from the issue text.