Add merge insertion sort (#2211)

* Add merge insertion sort

* Fix python naming conventions

* Add wikipedia link

* Add type hint

* Fix python to python3

Co-authored-by: Christian Clauss <[email protected]>

* Refactor doubled process in if-condition into one outside of if-condition

Co-authored-by: Christian Clauss <[email protected]>

* Refactor make python3 prior to python

Co-authored-by: Christian Clauss <[email protected]>

* Fix name of is_surplus into has_last_odd_item

* Add comment

* Fix long comment to shorten

Co-authored-by: Christian Clauss <[email protected]>