Integrate template icons

[pinussilvestrus]

Closes #106
Depends on bpmn-io/element-template-icon-renderer#2
Depends on bpmn-io/bpmn-js-properties-panel#641

[pinussilvestrus]

This is waiting for a new properties panel release, but I think we can still wait for the other improvements to be merged, e.g. bpmn-io/bpmn-js-properties-panel#648

Maybe we can simply use this branch for the overall version bumps before the release /cc @MaxTru @marstamm

[barmac]

The way the icons are implemented means:

1. I get both icons on canvas and in the properties panel header when I use camunda-bpmn-js
2. Same as above if I install bpmn-js-properties-panel and @bpmn-io/element-templates-icons-renderer in a project without camunda-bpmn-js
3. My properties panel displays the icon in the header but I cannot see it on canvas when I build custom bpmn-js project without @bpmn-io/element-templates-icons-renderer

Do we intend to keep (3)? Perhaps the icons renderer should be required as a part of the element templates module -> to be extracted to a separate element templates package in the future.

[pinussilvestrus]

I thought about this one and given the current situation (element-templates as part of the properties panel) I found it strange to include rendering parts in the properties panel. However, I'd love to see the element templates be a standalone module. We should definitely tackle this in Q2 IMHO.

[MaxTru]

@pinussilvestrus is out sick today, but this is super well prepared and the dependencies are met. I am marking this as ready for review.

[barmac]

We need to release and integrate another alpha of bpmn-js-properties-panel to merge it.

[MaxTru]

Back to draft. I realized, we should also bump prop-panel to integrate the latest fix

[MaxTru]

Icons arrived

[MaxTru]

Back to draft, waiting until we have https://camunda.slack.com/archives/CKGH9LR40/p1649155653797739 fixed

[MaxTru]

Works with fix :-)