added wikipedia link

[3NCRY9T3R]

• I have read freeCodeCamp's contribution guidelines.
• My pull request has a descriptive title (not a vague title like Update index.md)
• My pull request targets the master branch of freeCodeCamp.
• None of my changes are plagiarized from another source without proper attribution.
• My article does not contain shortened URLs or affiliate links.

If your pull request closes a GitHub issue, replace the XXXXX below with the issue number.

Closes #XXXXX

[RandellDawson]

Hi,

Thanks for this pull request (PR).

Unfortunately, we are marking this PR invalid for hacktoberfest. We believe it does not follow the recommended guidelines:

Quality Standards

In line with Hacktoberfest value #2 (Quantity is fun, Quality is key), we have provided examples of the quality standards we encourage. This applies mainly to beginners.

• PRs that are automated e.g. scripted opening PRs to remove whitespace / optimize images.
• PRs that are disruptive e.g. taking someone else's branch/commits and making a PR.
• PRs that are regarded by a project maintainer as a hindrance vs. helping.
• Something that's clearly an attempt to simply +1 your PR count for October.

Learn more at https://hacktoberfest.digitalocean.com/details