Revise, clean up content on Home Page

[Jaqster]

It would be good to go through and revise/clean up some of the tutorials, projects, and videos on the Home Page. Look for:

• Reduce the amount of words in each step of a tutorial (https://github.com/microsoft/pxt-microbit/issues/5064)
• Add rich media in modals (videos, gif/animations, images)
• Add code validation rules to tutorials
• Ensure correctness (using latest blocks/API's)

[abchatra]

@Jaqster Still planned?

[Jaqster]

Well, reorganizing the Home Page content, but not sure about updating all the tutorials... We talked about doing this in August before back-to-school.