Free software libraries used in this project:

CtxMenu by Nils Söderman (MIT) https://github.com/nils-soderman/CtxMenu-Javascript
graphlib by Chris Pettitt (MIT) https://github.com/dagrejs/graphlib/
LeaderLine by anseki (MIT) https://github.com/anseki/leader-line/
PlainDraggable by anseki (MIT) https://github.com/anseki/plain-draggable
VueJS by Yuxi Evan You (MIT) https://github.com/vuejs/