The if-check for arrowMarkerAbsolute in the flowchart-v2 code is in
dagre-wrapper. Unfortunately, I can't seem to find a way to find the
local conf (e.g. the one set via `flowRenderer.setConf()`, so instead
I'm using global mermaid config from `src/config`.
Flowchart v1 arrowMarkerAbsolute=true is still broken, but I'm not
really sure how to fix that.