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  <69459134+imSanko@users.noreply.github.com>

* 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

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Co-authored-by: Saptadeep Banerjee <69459134+imSanko@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>