Universal Process Notation (UPN) support

[mantielero]

It would be great being able to draw UPN diagrams with D2. They are used to describe processes in a simple way (as opposed to BPMN which is way more complex).

The spec is here -about 15 pages-.

And some examples (taken from this bug report:
https://elements.cloud/2016/06/01/upn/
https://www.salesforceben.com/introduction-to-universal-process-notation-upn-for-salesforce-processes-mapping/
https://www.tibco.com/resources/whitepaper/universal-process-notation-simple-solution-complex-process-diagrams

It looks pretty simple, compare to what D2 is already capable to do.

[dplassgit]

That's not really anything I'm interested in the language to do. Note, there is already interop with C libraries so it's possible to use extern to call an external library already.

[thekalinga]

@mantielero You seemed to have opened the issue in the wrong d2 project. You seemed to have already raised one there too.

[mantielero]

Oops. I don't know how I mixed this up. Sorry guys for the noise. And good luck with your project.