chore: add lab for linked list in frontend cert(JS only)

[jdwilkin4]

There will be lectures videos to talk about different common data structures, and big O. But we need a lab for them to do it themselves.

In the coding interview prep section, we already have these interactive challenges https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/create-a-linked-list-class https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/search-within-a-linked-list

Convert those challenges, into the lab format. The user stories should have them doing the following

• create a linked list class
• have them create head and size methods
• have them create an add method
• have them create a remove method
• have them create an isEmpty method

Acceptance criteria

• [ ] create a new folder of the project in the frontend-cert/js-projects directory
• [ ] add your completed project in an script.js file in that new folder
• [ ] create a markdown file for your proposed user stories. You should call it user-stories.md and place it in your new project folder