Add DataFrame.merge() term entry

[Enrique-Macias]

Description

Added a new term entry for the DataFrame.merge() method in Pandas. The entry includes:

• A clear description of the merge() method and its purpose
• Detailed syntax section with all parameters explained
• Example demonstrating basic merge operation with output

Location: content/pandas/concepts/dataframe/terms/merge/merge.md

Issue Solved

Closes #6779

Type of Change

• Adding a new entry
• Editing an existing entry (fixing a typo, bug, issues, etc)
• Updating the documentation

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]

Hey @Enrique-Macias thank you for contributing to Codecademy Docs, the entry is nicely written! 😄

I've suggested a few changes, could you please review and modify those at your earliest convenience? Thank you! 😃

[Enrique-Macias]

Hi @mamtawardhani ,
Thank you for your feedback!
I’ve made the requested changes and pushed the updates to this branch.
Please let me know if there’s anything else I should address.
Thanks again for your review!

[mamtawardhani]

Thank you for the edits @Enrique-Macias 😄

The entry looks good for a second round of review! 🚀