[Term Entry] CSS Margins: margin-inline

[Utkarsh-Singhal-26]

Description

This PR adds a new term entry for the margin-inline property in CSS positioning concept.

Changes made:

• Created a new file: docs/content/css/concepts/margins/terms/margin-inline/margin-inline.md
• Added an introduction explaining the margin-inline property
• Included a Syntax section with clear parameter description
• Provided an Example section demonstrating practical usage of the property with multiple margin-inline examples
• Showed how elements are inserted at the beginning of the queue

Issue Solved

Closes #8212

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.