feat: add callback to updateContainer (#2406)

* add an optional callback to updateContainer. This is useful so we can figure out when react is done building the page.

* add changeset

.changeset/smooth-dolphins-tap.md

@@ -0,0 +1,5 @@
+---
+'@react-pdf/renderer': patch
+---
+
+Added an optional callback to the updateContainer method. This allows the user of the pdf instance to know when the update operation is finished in React. As this is an optional argument, no user code should be changed.

packages/renderer/index.d.ts

@@ -511,7 +511,7 @@ declare namespace ReactPDF {
     toBlob: () => Promise<Blob>;
     toBuffer: () => Promise<NodeJS.ReadableStream>;
     on: (event: 'change', callback: () => void) => void;
-    updateContainer: (document: React.ReactElement<any>) => void;
+    updateContainer: (document: React.ReactElement<any>, callback?: () => void) => void;
     removeListener: (event: 'change', callback: () => void) => void;
   };
 

packages/renderer/src/index.js

@@ -25,8 +25,8 @@ const pdf = initialValue => {
   renderer = renderer || createRenderer({ onChange });
   const mountNode = renderer.createContainer(container);
 
-  const updateContainer = doc => {
-    renderer.updateContainer(doc, mountNode, null);
+  const updateContainer = (doc, callback) => {
+    renderer.updateContainer(doc, mountNode, null, callback);
   };
 
   if (initialValue) updateContainer(initialValue);