(core) Making side bars a bit more usable for narrow screen

Summary:
 - closes side bars when tapping content area
 - opens left panel when tapping the page name

Test Plan: Includes browser tests.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2705

app/client/ui/AppUI.ts

@@ -149,6 +149,6 @@ function pagePanelsDoc(owner: IDisposableOwner, appModel: AppModel, appObj: App)
     onResize,
     testId,
     optimizeNarrowScreen: true,
-    contentBottom: dom.create(createBottomBarDoc, pageModel)
+    contentBottom: dom.create(createBottomBarDoc, pageModel, leftPanelOpen, rightPanelOpen)
   });
 }