(core) Update onboarding flow

Summary:
A new onboarding page is now shown to all new users visiting the doc
menu for the first time. Tutorial cards on the doc menu have been
replaced with a new version that tracks completion progress, alongside
a new card that opens the orientation video.

Test Plan: Browser tests.

Reviewers: jarek

Reviewed By: jarek

Differential Revision: https://phab.getgrist.com/D4296

app/client/ui2018/IconList.ts

@@ -133,13 +133,17 @@ export type IconName = "ChartArea" |
   "Separator" |
   "Settings" |
   "Share" |
+  "Skip" |
   "Sort" |
   "Sparks" |
+  "Star" |
   "Tick" |
   "TickSolid" |
   "Undo" |
   "Validation" |
   "Video" |
+  "VideoPlay" |
+  "VideoPlay2" |
   "Warning" |
   "Widget" |
   "Wrap" |
@@ -290,13 +294,17 @@ export const IconList: IconName[] = ["ChartArea",
   "Separator",
   "Settings",
   "Share",
+  "Skip",
   "Sort",
   "Sparks",
+  "Star",
   "Tick",
   "TickSolid",
   "Undo",
   "Validation",
   "Video",
+  "VideoPlay",
+  "VideoPlay2",
   "Warning",
   "Widget",
   "Wrap",