pandas-dev#39367 DOC: split contributing.rst (pandas-dev#40130)

* pandas-dev#39367 DOC: split contributing.rst

* DOC: attempt to fix broken refs

* DOC: attempt to fix broken refs

* DOC: attempt to fix broken refs

* DOC: attempt to fix broken refs

* DOC: fix spelling

* DOC: fix spelling

* DOC: remove trailing whitespace

* Update doc/source/development/env_outside_docker.rst

Co-authored-by: Daniel Saxton <[email protected]>

* DOC: restructure enviroment setup as new file

* DOC: updated files

* DOC: fix link

Co-authored-by: Daniel Saxton <[email protected]>
Co-authored-by: Marco Gorelli <[email protected]>

Author: 3 people