Feat: Add Exercise Page

[syke9p3]

Description

This PR adds a new Exercise page to display information about each exercise in the Guide Page.

Changes made

ExercisePage.jsx Created a new exercise page containing the exercise steps, image, YouTube video, and name of contributor.

App.jsx Added a new route for the new exercise page.

Card.jsx Made each exercise Card clickable by wrapping the Cards in a Link component that brings you to each exercise page.

YoutubeEmbed.jsx Added a responsive YouTube embedded player to render YouTube video links.

Related Issue

Relates to #288

Screenshot