Created term entry for .assign() method for C++ strings

[em07-adoz]

Description

I created a term entry for the C++ strings .assign() method. My motivation for doing this was a a part of the my project for the Write Tech Bootcamp that I took to learn Technical Writing .

Issue Solved

Closes #7094 [Term Entry] C++ Strings: assign()

Type of Change

• Adding a new entry

• Adding a new entry
• Editing an existing entry (fixing a typo, bug, issues, etc)
• Updating the documentation

Checklist

• [ x] All writings are my own.
• [ x] My entry follows the Codecademy Docs style guide.
• [ x] My changes generate no new warnings.
• [x ] I have performed a self-review of my own writing and code.
• [ x] I have checked my entry and corrected any misspellings.
• [ x] I have made corresponding changes to the documentation if needed.
• [ x] I have confirmed my changes are not being pushed from my forked main branch.
• [x ] I have confirmed that I'm pushing from a new branch named after the changes I'm making.
• [x ] I have linked any issues that are relevant to this PR in the Issues Solved section.