Added code and readme for first and last position of element in sorted array

[suburban-daredevil]

Find First and Last Position of Element in Sorted Array

Question number - 34

Issue no.(must) - #21

Closes #21

Self Check(Tick After Making pull Request)

• [x] This issue was assigned to me.
• [x] One Change in one Pull Request
• [x] My file is in proper folder (Name of folder should be Question number) (E.g. 120)
• [x] I am following clean code and Documentation and my code is well linted with flake8.
• [x] I have added README.md (With question description)
• [x] I have added sufficient comments in my code

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[suburban-daredevil]

Hey @pawangeek . This PR resolves #21 . Thanks!

[suburban-daredevil]

Hey @pawangeek . Thanks!