DOC: add animations.css

[AKSHITHA-CHILUKA]

What's wrong with the existing documentation

add custom CSS animations that can be used throughout the site.

File to change

adding new file

Details of the change

animations to be added

Type of change

adding new sections

Record

• [X] I agree to follow this project's Code of Conduct
• [X] I'm a GSSOC'24 contributor
• [X] I want to work on this issue

[minakshikr7]

Please assign me this issue under @GSS0C24