Decouple @craftjs/layers with styled-components

[addlistener]

My project does not depend on styled-components, however @craftjs/layers will depend on it even tho I provide a custom render. The same thing applies to react-contenteditable.

craft.js/packages/layers/src/layers/DefaultLayer/DefaultLayerHeader.tsx

Line 3 in 46eb68e

import styled from 'styled-components';

Ideally the @craftjs/layers should be headless? I guess we can move the default layer component inside the examples?

[addlistener]

Plus there are some warnings here because of the UI. A bit annoying lol