docs: fix scrollPerPage default value

[takumiz19]

fix scrollPerPage default value

Description

https://github.com/SSENSE/vue-carousel/blob/master/src/Carousel.vue#L293-L296 I fixed docs because default value of scrollPerPage is true in this source code.

Motivation and Context

issue is here https://github.com/SSENSE/vue-carousel/issues/494

Types of changes

• [x] 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)

Checklist:

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