Add nodes with render and transform

src/nodes/StringNode.ts

@@ -0,0 +1,11 @@
+import { AbstractNode, NodeMods } from './AbstractNode'
+
+export class StringNode extends AbstractNode<string> {
+  constructor(mods?: NodeMods<string>) {
+    super(mods)
+  }
+
+  render(field: string, value: string) {
+    return `<span>${field}</span> <span>${value || ''}</span>`
+  }
+}