First version of the css background-position-x property markdown

[CaptainTech205]

Description

Created a new directory "background-position-x" in codecademy_docs\content\css\concepts\background\terms and a new file within that directory called "background-position-x.md". The markdown file describes the CSS property background-position-x and shows syntax and example.

Issue Solved

Closes #8197

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.