OpenSCD next architecture

Motivation for creating a new generation of OpenSCD:

1. Make is more easy to build your own distribution
2. Make is more easy to create custom plug-ins
3. Less tangled code
4. Reuseable code
5. Faster development speed (once it is ready)

Practical example for CoMPAS. CoMPAS currently relies on fork of OpenSCD in order to add the needed functionality:

com-pas/compas-open-scd: A substation configuration description editor for projects using SCL IEC 61850-6 Edition 2 or greater (github.com)

The goal for CoMPAS would be to add the CoMPAS specific code as add-on to OpenSCD-next in form of plug-ins. The current "fork" will no longer be needed. CoMPAS will just make a distribution of OpenSCD including the CoMPAS plugins/extensions.