[feat]: add group prop

[logaretm]

This PR implements the group prop using an event bus instead of component references.

Checklist

• Implement group prop.
• Update docs.

Overview

Carousels can now be synced no matter how deeply nested inside other components, it also supports binding the group prop to get dynamic groups working.

This PR addresses the goals in #94 :

• Ability to sync more than two carousels.
• Syncing carousels will be context independent.
• Fix issue when passing carousel to another component slot.

Example usage:

<hoooper group="myCarousel">
    ...
</hooper>

<hoooper group="myCarousel">
    ...
</hooper>

<hoooper group="myCarousel">
    ...
</hooper>

PS: This PR removes some unused dependencies due to Vuepress 1.x upgrade.

Issues affected

closes #94
closes #69
closes #55

[ismail9k]

It looks like you are using a different lint setup⁠ (using double quotes, and space after function declaration⁠, ...). So please include your lint setting file, to have a consistent style all over the project.

[logaretm]

@abdelrahman3d I have updated the linting config as requested.