Link catch events are added below the start event, not modeled backwards

[till-stadtler]

Describe the Bug

This is related to example 2 in the PR #56. The current version does not implement backwards modeling correctly:

The depicted issue will happen as soon as a link catch event is used after any elements with column height greater than 1.

Steps to Reproduce

1. Navigate to https://bpmn-io.github.io/bpmn-auto-layout/
2. Model a link catch event behind elements with column height greater than 1.

Expected Behavior

I expect the link catch event to be modeled backwards from the merging gateway.

Environment

https://bpmn-io.github.io/bpmn-auto-layout/

[abdul99ahad]

Adding to ready state.