feat: support {{block.super}}, see #38

src/drop/block-drop.ts

@@ -0,0 +1,13 @@
+import { Drop } from './drop'
+
+export class BlockDrop extends Drop {
+  constructor (
+    // the block render from layout template
+    private superBlockRender: () => Iterable<string> = () => ''
+  ) {
+    super()
+  }
+  public super () {
+    return this.superBlockRender()
+  }
+}