Advance HTML and CSS: Adding solar system project

[BUTURUM]

Because

The contributors discussed and found adding missing project in Animation section of Advance HTML and CSS course necessary in issues #28000 and #26390.

Adding solar system project as project for Animation section, allows learners to practice keyframes and transition by building project that they can realistically be asked to do in real life. That naturally forces them to face more realistic challenges and (in my humble opinion) more interesting.

This PR

• Adds Solar System project in Animation section of Advance HTML and CSS course.

Issue

Closes #28000

Additional Information

I am admittedly not the best writer, thus writing quality of project-lesson might be lacking. Any criticism of my writing is welcomed and even needed. I am also not sure if I gave learners too much or not enough guidance in this lesson, so please commend on that.

I also updated my demo to comply with @thatblindgeye's corrections discussed in #28000.

Pull Request Requirements

• I have thoroughly read and understand The Odin Project curriculum contributing guide
• The title of this PR follows the location of change: brief description of change format, e.g. Intro to HTML and CSS lesson: Fix link text
• The Because section summarizes the reason for this PR
• The This PR section has a bullet point list describing the changes in this PR
• If this PR addresses an open issue, it is linked in the Issue section
• If any lesson files are included in this PR, they have been previewed with the Markdown preview tool to ensure it is formatted correctly
• If any lesson files are included in this PR, they follow the Layout Style Guide