Be able to link resources in process application

[philippfromme]

Problem you would like to solve

In a process application users should be able to link BPMN processes, DMN diagrams and forms similar to the web modeler.

In the web modeler you can link by

• using the properties panel
  • resources that can be linked aren't shown (e.g. through autocomplete)
  • no validation of linked resource

• using overlay
  • resources that can be linked are shown
  • validation of linked resource

Proposed solution

• resources can be linked to each other
• resource links will be linted
  • broken resource links will be shown in Problems tab
• to be decided
  • how can resources be linked
    • properties panel only (autocomplete could be added)
    • overlay

User flow

Linking could be implemented without any new UI using autocomplete.

Alternatives considered

None.

Additional context

Related to #2508

[philippfromme]

Related to bpmn-io/bpmn-js-properties-panel#708