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/Explorer/Notebook/NotebookComponent/NotebookComponentAdapter.tsx

@@ -1,14 +1,11 @@
-import * as React from "react";
-
-import { ReactAdapter } from "../../../Bindings/ReactBindingHandler";
-import { NotebookClientV2 } from "../NotebookClientV2";
-
 // Vendor modules
 import { actions, createContentRef, createKernelRef, selectors } from "@nteract/core";
-import VirtualCommandBarComponent from "./VirtualCommandBarComponent";
+import * as React from "react";
+import { ReactAdapter } from "../../../Bindings/ReactBindingHandler";
+import { NotebookClientV2 } from "../NotebookClientV2";
 import { NotebookContentItem } from "../NotebookContentItem";
 import { NotebookComponentBootstrapper } from "./NotebookComponentBootstrapper";
-import { CdbAppState } from "./types";
+import VirtualCommandBarComponent from "./VirtualCommandBarComponent";
 
 export interface NotebookComponentAdapterOptions {
   contentItem: NotebookContentItem;
@@ -19,7 +16,6 @@ export interface NotebookComponentAdapterOptions {
 
 export class NotebookComponentAdapter extends NotebookComponentBootstrapper implements ReactAdapter {
   private onUpdateKernelInfo: () => void;
-  public getNotebookParentElement: () => HTMLElement;
   public parameters: any;
 
   constructor(options: NotebookComponentAdapterOptions) {
@@ -46,11 +42,6 @@ export class NotebookComponentAdapter extends NotebookComponentBootstrapper impl
         })
       );
     }
-
-    this.getNotebookParentElement = () => {
-      const cdbAppState = this.getStore().getState() as CdbAppState;
-      return cdbAppState.cdb.currentNotebookParentElements.get(this.contentRef);
-    };
   }
 
   protected renderExtraComponent = (): JSX.Element => {