feat: add example

[philippfromme]

Proposed Changes

Adds an interactive example available through npm start.

Checklist

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

• [x] Brief textual description of the changes present
• [x] Visual demo attached
• [x] 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]

Awesome stuff!

Isolated example via https://github.com/bpmn-io/bpmn-auto-layout/pull/60/commits/db4ff4ed3b69e202fbb104c3229a8bdbf4622bd2, and added ability to deploy it: https://github.com/bpmn-io/bpmn-auto-layout/pull/60/commits/77c22817e6128d1b04e6634ebe3e8bec18a313c9.

[nikku]

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