Nodes selection store, linking and unlinking nodes

src/Graphviz.tsx

@@ -15,7 +15,9 @@ export function graphToDot(g) {
 
   // edges
   for (const e of g.edges) {
-    lines.push(`  \"${e.from}\" -> \"${e.to}\";`);
+    const attrs = [];
+    attrs.push(`id=\"${e.id}\"`)
+    lines.push(`  \"${e.from}\" -> \"${e.to}\" [${attrs.join(', ')}];`);
   }
 
   // close