Added doctest to skew_heap.py (#11147)

* Added doctest to skew_heap.py

* Update skew_heap.py

* Update data_structures/heap/skew_heap.py

Co-authored-by: Saptadeep Banerjee  <[email protected]>

* Update skew_heap.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update skew_heap.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: Saptadeep Banerjee <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>