GLSP-1692: Fix elkfactory for browser usecase

[tortmayr]

What it does

Replace no-op elk factory with proper setup for isWebworker context. A small workaround/hack is required to present a document during construction of the factory which routes elkjs to the c orrect in-process message worker

Fixes eclipse-glsp/glsp#1692

How to test

• To test locally, checkout glsp-client master alongside the server-node repo and run

yarn dev:browser --external-server /path/tp/glsp-server-node/examples/workflow-server-bundled-web/wf-glsp-server-webworker.js

Then trigger a layout via Ctrl+Shift+L

I have already verified this locally. It might be easier to simple merge this after a positive code reivew and directly test in the glsp-client repo without the --external-server workaround.

Follow-ups

Changelog

• This PR should be mentioned in the changelog
• This PR introduces a breaking change (if yes, provide more details below for the changelog and the migration guide)
  Replaces the no-op webworker in the browser context with an actual working implementation.
  Adopters that relied on the fact that the elkLayoutModule was effectivly no-op in the browser might need to adopt accordingly