Add missing Shell Sort algorithm

[ABHIRANJAN-KUMAR1]

Repository commit

a0b0f41ae134aa1772d33bb930e5a960f9979e8

Python version (python --version)

Python 3.10.7

Dependencies version (pip freeze)

appnope==0.1.3
asttokens==2.0.8
backcall==0.2.0
decorator==5.1.1
executing==0.8.3
matplotlib-inline==0.1.6
parso==0.8.3
pexpect==4.8.0
pickleshare==0.7.5
prompt-toolkit==3.0.36
ptyprocess==0.7.0
pure-eval==0.2.2
Pygments==2.14.0
six==1.16.0
stack-data==0.2.0
traitlets==5.1.1
wcwidth==0.2.5

Expected behavior

The Shell Sort algorithm should be implemented correctly in the repository.
When a list is given as input, it should return the sorted list in ascending order.

Actual behavior

There is currently no Shell Sort algorithm implemented in the repository.