Refactor views to support dynamic updates.

src/card-controller/view/modifiers/substream-select.ts

@@ -0,0 +1,15 @@
+import { setSubstream } from '../../../utils/substream';
+import { View } from '../../../view/view';
+import { ViewModifier } from '../types';
+
+export class SubstreamSelectViewModifier implements ViewModifier {
+  protected _substreamID: string;
+
+  constructor(substreamID: string) {
+    this._substreamID = substreamID;
+  }
+
+  public modify(view: View): void {
+    setSubstream(view, this._substreamID);
+  }
+}