Add image placeholder and upload indicating frame (#1666)

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>
Co-authored-by: Philip Molares <philip.molares@udo.edu>

src/components/markdown-renderer/utils/node-to-react-transformer.tsx

@@ -31,6 +31,13 @@ export class NodeToReactTransformer {
     this.replacers = replacers
   }
 
+  /**
+   * Resets all replacers before rendering.
+   */
+  public resetReplacers(): void {
+    this.replacers.forEach((replacer) => replacer.reset())
+  }
+
   /**
    * Converts the given {@link Node} to a react element.
    *