docs: Add C++ unordered_set::count() term entry (#8027)

[Rishabh1925]

Closes #8027

This PR adds the documentation entry for the C++ unordered_set::count() method.

Implementation Details:

• File Path: Created the file at the required location: docs/content/cpp/concepts/unordered-set/terms/count/count.md.
• Core Concept: The entry clarifies that due to the uniqueness constraint of unordered_set, .count() will only ever return 1 (found) or 0 (not found).
• Structure: Includes the mandatory Description, Syntax, and Example sections.
• Codebyte: Included a Codebyte section with compilable C++ code for searching elements, meeting all issue requirements.

[Rishabh1925]

Hey @mamtawardhani @codecademy-docs

I've finished creating the new term entry for unordered_set::count(). The entry includes the required Codebyte and focuses on clarifying the method's unique return values (0 or 1). Ready for review!

[Rishabh1925]

Hey @mamtawardhani please look into this issue and merge this please, after which i can move to more issues.

Thanks a lot

[mamtawardhani]

Looks good for a second review! 🚀

[Rishabh1925]

@mamtawardhani @dakshdeepHERE Please look into this PR.....and merge this please

[Rishabh1925]

Hello @mamtawardhani @Sriparno08

Can you please merge this PR, it has been hanging here for too long now I think.

[Sriparno08]

Looks good, @Rishabh1925!

[github-actions]

👋 @Rishabh1925
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