feat: complete on blur / focusout

[nikku]

Proposed Changes

Allows user land to drop hacks that were previously needed to handle "complete on blur" in user land.

Related to bpmn-io/bpmn-js#2327

Checklist

To ensure you provided everything we need to look at your PR:

• Brief textual description of the changes present
• Visual demo attached
• Steps to try out present, i.e. using the @bpmn-io/sr tool
• Related issue linked via Closes {LINK_TO_ISSUE} or Related to {LINK_TO_ISSUE}

[nikku]

This is now back to backlog, paused for the moment. Need to spend more time on the bpmn-js (and other libraries) integration.