Added ShellSort in cpp

[DivasGupta7]

Related Issue

ShellSort

• Info about the related issue

• Closes: #[issue number that will be closed through this PR]

  49

  Describe the changes you've made

  I've added my shell sort in CPP

  Added Shell Sort algorithm in CPP with a clear understanding. I've commented out before every step wherever necessary.

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Original	Updated
original screenshot	updated screenshot

[rakesh0x7]

Hey @DivasGupta7 Please don't make PR directly! comment or raise an issue first!