Add option to return index in linear search

[darshan2456]

Resolves #1544

I changed the linear_search() to return index and -1 if element is not found. I am taking user input as to if they want to see the index and as per user input, i have branched the execution flow with a simple if statement.

• Added description of change
• PR title follows semantic commit guidelines
• Search previous suggestions before making a new one, as yours may be a duplicate.
• I acknowledge that all my contributions will be made under the project's license.

[github-actions]

This pull request has been automatically marked as abandoned because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.