[Concept Entry] C++ Unordered set unordered_set

[codecademy-gh-api]

Reason/inspiration (optional)

We would like a new entry on the Unordered_Set in C++. The entry should go in a new file under docs/content/cpp/concepts/unordered-set/unordered-set.md.     

The entry should include:    

• An introduction to the concept    
• A Syntax section that provides the syntax for the concept (if applicable)    
• An Example section that provides an example demonstrating the concept in use (if applicable)   
• An Codebyte Example section that provides an example demonstrating how to use Unordered set

Please refer to the concept entry template, content standards, and markdown style guide when working on the PR for this issue.|

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New Concept Entrty for Existing Topic

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[Jack-Race]

Hiya, can I work on this issue for the git&github course

[SaviDahegaonkar]

Hey @Jack-Race ,
You’re assigned 🎉 In addition to the documents linked in the description, please also look at the Contribution Guide. After creating a PR, the maintainer(s) (with the collaborator label) will add comments/suggestions to address any revisions before approval.

Is this your first contribution to Codecademy Docs? If so, we’re curious to know how you found out about contributing to Docs.

Thanks & Regards,
Savi