tsc fixes and rules

src/Graphviz.tsx

@@ -1,4 +1,6 @@
-export function graphToDot(g) {
+import type { GraphModel } from "./components/Graph";
+
+export function graphToDot(g: GraphModel): string {
   // Directed graph, use neato layout so we can use pos attributes
   const lines = [];
   lines.push('digraph G {');