Upsell for arc uiqr in Flipper plugin UI

Summary:
This diff updates the Flipper plugin for UIQR+DDR to upsell people to use `arc uiqr` on the "Upload and Get Link" tab. At the moment I'm not showing the upsell on the "Upload Screens to Diff" tab since this functionality isn't really supported through `arc uiqr` yet.

The upsell uses localstorage to maintain its open/close state so it will show up by default but will be permanently dismissed (unless localstorage is cleared somehow :) ).

NOTE: I hacked out this UI using some existing reusable UIQR Flipper components and some extra styling for the background, but definitely open to feedback on the UI!

Differential Revision: D38232117

fbshipit-source-id: e1745e32974bd9e750bbbaaa2f47bafdd0ac87eb

desktop/static/icons.json

@@ -112,6 +112,7 @@
     24
   ],
   "cross": [
+    12,
     16
   ],
   "dashboard-outline": [
@@ -642,4 +643,4 @@
   "app-instagram": [
     16
   ]
-}
+}