Gazler
fix(gemspec): update and amend installation
The previously used definitions did not yield an executable in Ubuntu 22.04 LTS. An explicit note to the license was added.
This PR is in partial fulfillment of #345 .
Tested in an instance of Linux Debian 13 / trixie (branch testing), as well as on an instance of Linux Xubuntu 22.04.2 LTS. It was the later where I had to modify the dependencies, I manually copy-pasted them as found on the log (cf log01.txt attached). Incrementally, I modified the file in question (i.e., for testing purposes, githug_edit.gemspec was replaced by githug_edit02.gemspec; the later now is the newly committed version of githug.gemspec). Tests were run once in Xubuntu (log02.txt) and Debian (log03.txt).