Graph Prop: isInteractive (#56)

* feat(props): add isInteractive

* refactor(selection): dont allow if not interactive

* feat(renderer): add class if is interactive

* chore(inactive): add tests

* refactor(inactive): no connection line, no edge selection

closes #49

example/src/index.css

@@ -1,3 +1,7 @@
+body {
+  font-family: sans-serif;
+}
+
 html, body {
   margin: 0;
 }