Allow new version of EDTF library

Problem/Motivation

The latest version of EDTF is 3.0.0. The release notes are in the README, here: https://github.com/ProfessionalWiki/EDTF. It looks compatible to me based on the release notes, but this module's composer.json needs to be updated to allow it.

Steps to reproduce

Try to install EDTF 3.0.0

Proposed resolution

Add a version constraint that allows 3.0.0 to composer.json