We add a dummy package github_cli for

• https://github.com/cli/cli#installation
• https://repology.org/project/github-cli/versions
  and add it to _develop's dependencies.

Thus it appears in the command lines in https://3b45534b5b3352783037dfc8b44a6590deca8100--sagemath-tobias.netlify.app/installation/source.html#software-prerequisites-and-recommended-packages
as well as in the conda environment file src/environment-dev.yml.

Depends on #34528
Depends on #34561
Depends on #33613

CC: @tobiasdiez @kwankyu @slel @dimpase @jhpalmieri

Component: packages: optional

Author: Matthias Koeppe

Branch/Commit: abb0f5f

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/34523