Add zunzun intro slides (issue 50)

[hakdo99]

The changes I made:

• Added the ZunZun intro slides (4 first slides in the "slides" array) to the mock-data.js file
• Commented out the "width" line in buttonNav in the index.tsx file to make the CTA button's width not extended to the screen's full width Note:
• The CTA button is currently moving relative to the intro text instead of staying in the same place in the bottom like in the design
• The CTA text is still Continue x 5 -> Let's get started