Kp/contributing consolidation in dev guide (#26)

* Consolidate all contributing and dev practices in the PyAnsys Developer User's Guide

* Consolidate all contributing and dev practices in the PyAnsys Developer User's Guide

* Fix bad spacing in dev_practices.rst

* Fix testing link.

* fix another bad link for testing

* Fix bad link to dev practices from contirbuting.rst

* Apply suggestions from code review

Co-authored-by: Maxime Rey <[email protected]>

Co-authored-by: Maxime Rey <[email protected]>

Author: PipKat