update README.md

[annabelaruiz111]

Description

Created introduction, features, and requirements sections to README.md, and added clarifications and elaborations to existing sections.

Motivation and Context

This change makes using Vue-Carousel more accessible by providing a more detailed explanation of the features it provides and how to use them.

How Has This Been Tested?

This commit was not tested since it was a documentation only change.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation change

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have included a vue-play example (if this is a new feature)