Add term entry for NumPy .where() built-in function

[jlima-geol]

Description

This PR adds a new term entry for the NumPy .where() built-in function, as requested in issue #6648.

The Markdown file follows the Codecademy Docs term entry template and includes:

• An introduction to the .where() function
• Syntax section
• Example section demonstrating basic use
• Codebyte Example for interactive testing

All formatting and style guidelines were followed using the recommended tooling (yarn format:verify and yarn format:all).

Issue Solved

Closes issue #6648

Type of Change

This PR adds a new term entry for the NumPy .where() built-in function, as requested in issue #6648.

The entry includes:

• Introduction
• Syntax
• Example
• Codebyte Example

Content follows the term entry template and Codecademy Docs style guidelines.

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 round of review! 🚀