Fix bug publish screenshot (#762)

[Preview this branch](https://cosmos-explorer-preview.azurewebsites.net/pull/762?feature.someFeatureFlagYouMightNeed=true)

The main change in this PR fixes the snapshot functionality in the Publish pane-related components. Because the code cell outputs are now rendered in their own iframes for security reasons, a single snapshot of the notebook is no longer possible: each cell output takes its own snapshot and the snapshots are collated on the main notebook snapshot.
- Move the snapshot functionality to notebook components: this removes the reference of the notebook DOM node that we must pass to the Publish pane via explorer.
- Add slice in the state and actions in notebook redux for notebook snapshot requests and result
- Add post robot message to take snapshots and receive results
- Add logic in `NotebookRenderer` to wait for all output snapshots done before taking the main one collating.
- Use `zustand` to share snapshot between Redux world and React world. This solves the issue of keeping the `PanelContainer` component generic, while being able to update its children (`PublishPanel` component) with the new snapshot.

Additional changes:
- Add `local()` in `@font-face` to check if font is already installed before downloading the font (must be done for Safari, but not Edge/Chrome)
- Add "Export output to image" menu item in notebook cell, since each cell output can take its own snapshot (which can be downloaded)
![image](https://user-images.githubusercontent.com/21954022/117454706-b5f16600-af46-11eb-8535-6bf99f3d9170.png)

src/CellOutputViewer/CellOutputViewer.tsx

@@ -9,11 +9,17 @@ import postRobot from "post-robot";
 import * as React from "react";
 import * as ReactDOM from "react-dom";
 import "../../externals/iframeResizer.contentWindow.min.js"; // Required for iFrameResizer to work
+import { SnapshotRequest } from "../Explorer/Notebook/NotebookComponent/types";
 import "../Explorer/Notebook/NotebookRenderer/base.css";
 import "../Explorer/Notebook/NotebookRenderer/default.css";
+import { NotebookUtil } from "../Explorer/Notebook/NotebookUtil";
 import "./CellOutputViewer.less";
 import { TransformMedia } from "./TransformMedia";
 
+export interface SnapshotResponse {
+  imageSrc: string;
+  requestId: string;
+}
 export interface CellOutputViewerProps {
   id: string;
   contentRef: ContentRef;
@@ -62,6 +68,36 @@ const onInit = async () => {
       ReactDOM.render(outputs, document.getElementById("cellOutput"));
     }
   );
+
+  postRobot.on(
+    "snapshotRequest",
+    {
+      window: window.parent,
+      domain: window.location.origin,
+    },
+    async (event): Promise<SnapshotResponse> => {
+      const topNode = document.getElementById("cellOutput");
+      if (!topNode) {
+        const errorMsg = "No top node to snapshot";
+        return Promise.reject(new Error(errorMsg));
+      }
+
+      // Typescript definition for event is wrong. So read props by casting to <any>
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      const snapshotRequest = (event as any).data as SnapshotRequest;
+      const result = await NotebookUtil.takeScreenshotDomToImage(
+        topNode,
+        snapshotRequest.aspectRatio,
+        undefined,
+        snapshotRequest.downloadFilename
+      );
+
+      return {
+        imageSrc: result.imageSrc,
+        requestId: snapshotRequest.requestId,
+      };
+    }
+  );
 };
 
 // Entry point