Count (#2084)

* Add files via upload

* Update and rename count_islands.py to count_islands_in_matrix.py

* Update matrix/count_islands_in_matrix.py

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

* Update matrix/count_islands_in_matrix.py

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

* Update matrix/count_islands_in_matrix.py

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

* Reformat count islands.py

* Indent Python code with 4 spaces, not tabs

* Update count_islands_in_matrix.py

* Add type hints for return values

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