Graph coloring (#1921)

* add skeleton code

* add doctests

* add mainc function pseudo code and tests (ToDo: write Implementation)

* typo fixes

* implement algorithm

* add type checking

* add wikipedia link

* typo fix

* update range syntax

Co-authored-by: Christian Clauss <cclauss@me.com>

* change indexed iteration checking to any()

Co-authored-by: Christian Clauss <cclauss@me.com>

* fix: swap import and documentation sections

* fix: change return none to return empty list

* remove unnecessary import (Union)

* change: remove returning boolean indicating problem was solved or not

* remove unnecessary import (Tuple)

Co-authored-by: Christian Clauss <cclauss@me.com>