Added replaceAll() term in javascript/strings

[JoyelJohny]

Description

• Adding replaceAll.md which consist of replaceAll strings method of the topic Javascript

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.
• Under "Development" on the right, I have linked any issues that are relevant to this PR (write "Closes # in the "Description" above).

[CLAassistant]

All committers have signed the CLA.

[SSwiniarski]

@JoyelJohny I did a first review and left a few comments.

[SSwiniarski]

@JoyelJohny Looks good for a second review.

[github-actions]

👋 @JoyelJohny
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