Update to paged.js 4

[cderv]

Announcement: https://pagedjs.org/posts/paged-break-the-long-overdue-update/

Some breaking change to take into account (from mattermost)

Paged.js version 4.0 is there with a breaking change: if you’re using the polyfill and call from the CDN, you will have some trouble in previewing page on screen.

You can

• stick to paged.js 0.3.5 and use this URL → https://unpkg.com/[email protected]/dist/paged.polyfill.js
• update the interface.css to use https://gitlab.coko.foundation/pagedjs/interface-polyfill/blob/master/interface.css this one