[FEAT] review sequence flow arrow rendering incoming to end event

[tbouffard]

Seen with version 0.1.2

We have introduced a larger stroke for end event and as the arrow is currently displayed in blue, we see that the arrow is not finishing before the event shape.
We could mitigate this by setting the spacing parameter of the mxArrow or mxArrowConnector shapes (set to 0 by default)

This may be review as part of #200

Notice that we see the same kind of behaviour with the bpmn.io solution

[csouchet]

• When I change only the Stroke width of the End event, we see that the edge ends exactly on the stroke of the shape of the End event :

• When I add only targetPerimeterSpacing=10 on the style of the edge, we see that the edge ends at the same place as before, but the edge (not the arrow) ends in the middle of the stroke of the shape of the End event :

=> So I think that MxGraph enlarges the shapes from the outside when the stroke is enlarged, and not from the inside :'(

[tbouffard]

Highly visible in v0.24.1 on the demo page with the dark theme and file A.4.0 (from miwg-test-suite)