Add NumPy ndarray.nonzero() term entry following Codecademy Docs stan…

[shatakshi220805]

Description

This PR adds a new term entry for the numpy.ndarray.nonzero() method under content/numpy/concepts/ndarray/terms/nonzero/.

The entry follows Codecademy Docs standards for term entries, including proper metadata, syntax, example, and a runnable Codebyte example.

Related Issue

Fixes #<ISSUE_NUMBER>

Type of Change

• ✨ New term entry
• 🐛 Bug fix
• 🧹 Content update/refactor
• 🧪 Example improvement

Checklist

• Added a new .md file in the correct path (content/numpy/concepts/ndarray/terms/nonzero/nonzero.md)
• Followed the Codecademy Docs Style Guide
• Verified syntax highlighting and Markdown formatting locally
• Previewed and confirmed correct rendering using yarn dev
• Ensured metadata fields (Title, Description, Subjects, Tags, CatalogContent) follow the template

Screenshots
"Unable to run yarn dev as this repo doesn’t include a dev script. Added screenshot of Markdown file instead.”

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[mamtawardhani]

Hey @shatakshi220805, please sign the CLA. And it also looks like you've made a commit using your local id, so please sign the CLA using that as well