Redesign first and last page of each milestone

[NothingEverHappens]

What the issue is about

Here's how the first and the last page of each milestone look like:

The first one is not very pretty, and also looks different from the rest of the codelab.

The last one if very messy, and contains too much of unstructured information.

Both should be redesigned to be pretty consistent and informative.

What we currently have on the first slide:

• The name of the milestone (e.g. TypeScript)
• The description of the milestone (e.g. Angular is written in TypeScript. Learn more about the language basics.)
• Hint to use keyboard arrows for navigation (Use ← and → on your keyboard to navigate the slides.)
• Prerequisites (e.g. Basic understanding of JavaScript is required.)

What we currently have on the first slide:

• Some final words (e.g. Now you should know enough TypeScript to start learning Angular! Read more about TypeScript on TypeScript web site)
• callout to star on github ( This codelab is written in Angular and available on Github. Please ⭐ if you enjoyed it.)
• Description of the next step: (Next: Learn how to create your first Angular app!)
• Rate this lesson panel

Other notes

It should be safe to change/reorder/break into multiple slides or even remove some of this information