[Term Entry] PyTorch Tensor Operations: .add()

[karishma-battina]

Description

Introduce a new entry on the .add() term under PyTorch with introduction, syntax and example.
Created file: docs/content/pytorch/concepts/tensor-operations/terms/add/add.md

Issue Solved

Closes #6292

Type of Change

• New Term for Existing Concept 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.