[FEAT] Render Transaction Sub-Process

[csouchet]

Is your feature request related to a problem? Please describe. Render the BPMN Transaction Sub-Process.

The boundary of the Sub-Process will be double-lined to indicate that it is a Transaction (see Figure 10.33). A Transaction Sub-Process is a rounded corner rectangle that MUST be drawn with a double thin line.

Note for implementation See the development documentation for details. Some tasks that are part of the implementation

• Update the MxGraph Shape for the Transaction Sub-Process
• Update the snapshot of the e2e test for Transaction Sub-Process.
• Update the BPMN Support documentation for the Transaction Sub-Process

Depends on #307