...The core of Semagrams is just a library; in order to make it do things, one needs to create an "app" that uses it. Currently, the only app that is being developed is a Petri net editor, though this will soon change. In order to run the Petri net editor standalone, install Mill and npm, and then in one terminal in scala/ run mill --watch apps.petri.fullLinkJS and in another terminal in scala/ run npm run dev. The second command should print out a url that you can click on. You may have to run npm install before running npm run dev.