add python venv instructions to getting started page

docs/source/index.rst

@@ -72,13 +72,16 @@ After installing `git <https://git-scm.com/>`_ and `docker <https://www.docker.c
 
 .. code-block::
 
+   # Create and activate a python virtual environment
+   python -m venv ~/venv-colrev && source ~/venv-colrev/bin/activate
+
    # Install CoLRev
    pip install colrev
 
    # ... and start with the main command
    colrev status
 
-The CoLRev environment supports for the whole literature review process:
+The CoLRev environment supports the whole literature review process:
 
 .. figure:: ../figures/figure-docs.png
    :width: 600