added nbytes.md

[Ananya44444]

Description

This PR adds a new entry for the .nbytes attribute of a NumPy ndarray.

The new file is located at content/numpy/concepts/ndarray/terms/nbytes/nbytes.md.

It explains:

1. What the .nbytes attribute represents (total bytes consumed by array elements).
2. Its syntax.
3. An example using np.arange to show its calculation (size * itemsize).
4. A Codebyte example showing its use on a 2D array with a specific dtype (float32).

Issue Solved

Issue #7825

Type of Change

• Adding a new entry

Checklist

• All writings are my own.
• My entry follows the Codecademy Docs style guide.
• My changes generate no new warnings.
• I have performed a self-review of my own writing and code.
• I have checked my entry and corrected any misspellings.
• I have made corresponding changes to the documentation if needed.
• I have confirmed my changes are not being pushed from my forked main branch.
• I have confirmed that I'm pushing from a new branch named after the changes I'm making.
• I have linked any issues that are relevant to this PR in the Issues Solved section.

[CLAassistant]

All committers have signed the CLA.

[mamtawardhani]

Looks good for a second review! 🚀

[avdhoottt]

Excellent entry, LGTM!!

[github-actions]

👋 @Ananya44444
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