We add a conda enviroment that is meant for development, i.e. includes tools that one probably needs while working on sage development such as linters, ssh (for contributing to trac) etc.

Moreover, we extract the conda-related things from docs/bootstrap to a new bootstrap-conda script in order to simplify the conda workflow (see updated documentation).

Github workflow run: https://github.com/sagemath/sagetrac-mirror/actions/runs/2268985510

CC: @isuruf @dimpase @saraedum @mkoeppe @slel

Component: build

Author: Tobias Diez

Branch: 87f360c

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/33740