Add packaging for Debian based distributions.

This commit adds a script (`create-deb-pkg.sh`), which creates a deb package containing the fastfetch and flashfetch executables as well as the bash-completion file. The script must be executed in an environment, where `dpkg-deb` is present (a debian based environment).
Because Deb versioning is not compatible with fastfetch version strings, it is adapted to the format: `0:1$FF_VERSION-0`.

packaging/deb/control-template

@@ -0,0 +1,13 @@
+Package: fastfetch
+Version: <VERSION>
+Section: utils
+Priority: extra
+Architecture: amd64
+Maintainer: peter@bohner.me
+Homepage: https://github.com/LinusDierheimer/fastfetch
+Installed-Size: 410K
+Description: A fast alternative to neofetch
+ fastfetch is a neofetch-like tool for fetching system information and
+ displaying them in a pretty way. It is written in c to achieve much better
+ performance, in return only Linux and Android are supported. It also uses
+ mechanisms like multithreading and caching to finish as fast as possible.