feat: useLayers setting to manage z-index on dragging

[digitalclubb]

Overview

Adding a setting to manage z-index layering.

Current behaviour will apply a z-index when an item is selected and apply a high z-index when the item has been dragged. This setting would allow users to disable this behaviour so that items retain their original z-index.

Usage:

const ds = new DragSelect({
    selectables: document.getElementsByClassName('item'),
    area: document.getElementById('container'),
    useLayers: false,
})

Type of change

• ✨ Feature - a new component or behaviour has been added
• 🐛 Fix - fixing a known issue within the codebase
• ♻️ Chore - maintenance task where behaviour and implementation haven't changed
• 📝 Docs - updating any README or markdown files

Checklist

• I have updated the documentation accordingly.
• I have set the PR title to conventional commit format.
• I have built any changed GitHub Actions.

[ThibaultJanBeyer]

Awesome PR 🌟
Honestly this is the cleanest and most complete PR this library has ever gotten! Will merge and deploy immediately as is once tests have passed, thank you =)

[ThibaultJanBeyer]

Released in version 3.1.0. Thanks, your contribution is noted & appreciated <3