Add 3 New CSS Basics Challenges + New Demo End

The demo end state is updated and works with the new (reduced) and the old curriculum.

New Challenges ✨

`css-basics/pink-box`

📄 Rendered Exercise

🔎 Review

Review via 🔗 CodeSandbox or locally by running this command in your Terminal:

npx ghcd@latest neuefische/web-exercises/tree/css-basics-and-selectors/sessions/css-basics/pink-box -i

✨ Copyable Markdown for Curriculum

Solve this challenge on
[🔗 **CodeSandbox**](https://codesandbox.io/s/github/neuefische/web-exercises/tree/main/sessions/css-basics/pink-box?file=/README.md)
or locally by running this command in your Terminal:

npx ghcd@latest neuefische/web-exercises/tree/main/sessions/css-basics/pink-box -i

`css-basics/pseudo-park`

📄 Rendered Exercise

🔎 Review

Review via 🔗 CodeSandbox or locally by running this command in your Terminal:

npx ghcd@latest neuefische/web-exercises/tree/css-basics-and-selectors/sessions/css-basics/pseudo-park -i

✨ Copyable Markdown for Curriculum

Solve this challenge on
[🔗 **CodeSandbox**](https://codesandbox.io/s/github/neuefische/web-exercises/tree/main/sessions/css-basics/pseudo-park?file=/README.md)
or locally by running this command in your Terminal:

npx ghcd@latest neuefische/web-exercises/tree/main/sessions/css-basics/pseudo-park -i

`css-basics/combined-users`

📄 Rendered Exercise

🔎 Review

Review via 🔗 CodeSandbox or locally by running this command in your Terminal:

npx ghcd@latest neuefische/web-exercises/tree/css-basics-and-selectors/sessions/css-basics/combined-users -i

✨ Copyable Markdown for Curriculum

Solve this challenge on
[🔗 **CodeSandbox**](https://codesandbox.io/s/github/neuefische/web-exercises/tree/main/sessions/css-basics/combined-users?file=/README.md)
or locally by running this command in your Terminal:

npx ghcd@latest neuefische/web-exercises/tree/main/sessions/css-basics/combined-users -i

neuefische / web-exercises