fix(guide): Add full solution to jQuery challenge: Use jQuery to Modify the Entire Page

[thecodingaviator]

• 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.
• All the files I changed are in the same world language (for example: only English changes, or only Chinese changes, etc.)
• My changes do not use shortened URLs or affiliate links.

Closes #XXXXX

[RandellDawson]

@thecodingaviator When posting a full solution for the Guide, it should include all relative code (HTML, CSS, JS), so that a user could copy/paste and replace all the code in the editor and the code would pass.

[thecodingaviator]

@RandellDawson That goes for all guide articles, right? I was going by what the existing articles say and they had only the <script>

[RandellDawson]

@thecodingaviator The guide articles you find that do not have the full code should be updated at some point. We will just fix them as we find them.

[thecodingaviator]

Ahh, alright

[RandellDawson]

Thank you for your contribution to the page! 👍
We're happy to accept these changes, and look forward to future contributions. 🎉