Add "Nostalgic Tree" animation by CorySands

[CorySands]

Thank you for making a pull request to ZTM's Animation Nation project. We will review your pull request as soon as we can, but keep in mind we can get very busy during Hacktoberfest.

While you're waiting, please look over this checklist. Feel free to write a description of what you did as well!

What I did

Added animation named "Nostalgic Tree"

Pull request checklist

• This pull request uses HTML and CSS only and provides a meta.json file.
• All files in this pull request are in a directory named: <github_username>-<art_name> without the <>.
• Your pull request contains index.html and styles.css.
  • Your html file is named exactly: index.html
  • Your css file is named exactly: styles.css
• Your pull request your meta.json with:
  • githubHandle: being your unique github user name,
  • artName : name of your animation
• Your submission includes at least one animation.
• Your pull request does not modify any other files in the repository.

Not normally needed

• Check this if you would like to discuss an improvement besides adding animations

Note: if your pull request makes an improvement besides adding a CSS animation you will need to discuss this with the maintainers. You can help kickstart this process by explaining what your change does and why you are making it in the "What I did" section

What to expect

• If your pull request meets the checklist requirements it will be approved and merged by a maintainer
• If your pull request needs some changes. A maintainer will leave a comment requesting changes
• If your pull request significantly violates the criteria in the checklist it will be closed with feedback.