Added CSS translateZ() transform function documentation

[Tukesh1]

Description

Added a new term entry for the CSS translateZ() transform function. This entry includes:

• Comprehensive documentation explaining how translateZ() moves elements along the Z-axis in 3D space
• Proper syntax section with parameter details
• Two practical examples showing positive and negative Z-axis movement
• Important note about percentage values not being supported for Z-axis transformations

Issue Solved

Closes #7463

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.