Docs: Add binascii.a2b_base64() entry

[swayam-mishra]

Description

This pull request introduces a new term entry for the binascii.a2b_base64() function in Python, as part of a Hacktoberfest contribution.

The new file is located at content/python/concepts/binascii-module/terms/a2b-base64/a2b-base64.md. It includes a clear definition, syntax, a standard example with output, and a runnable Codebyte example, all structured according to the Codecademy Docs term entry template.

Issue Solved

Closes #7696

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! 🚀

[github-actions]

👋 @swayam-mishra
You have contributed to Codecademy Docs, and we would like to know more about you and your experience.
Please take a minute to fill out this four question survey to help us better understand Docs contributions and how we can improve the experience for you and our learners.
Thank you for your help!

🎉 Your contribution(s) can be seen here:

https://www.codecademy.com/resources/docs/python/binascii-module/a2b-base64

Please note it may take a little while for changes to become visible.
If you're appearing as anonymous and want to be credited, visit the linked accounts page and ensure that your GitHub account is linked.