Document how to use element templates

[nikku]

Is your feature request related to a problem? Please describe

We should not hide element templates as a feature, but encourage its use.

Describe the solution you'd like

• Create element template example, could be as simple as copying bpmn-js-connectors-extension example
• Connect with custom element examples; argue when to use what
• Link to element template documentation

Describe alternatives you've considered

None.

[nikku]

Requested again by a user in our forum.

[nikku]

Requested again via forum.