One of the takeaways of the mobile VE A/B test was that VE had a lower success rate than WTE, because it took longer to load, causing users to abandon their edit before even starting.
We should add a way to switch to WTE (which loads much faster) if the loading takes too long.
=== Deployment timing
Ideally, this patch will ride the train that goes out on !!10 Oct 2023!!.
=== Requirements
1. If after **3 seconds** mobile VE has not yet loaded, show people prompt this ticket is introducing
2. Prompt should read:
-- `Slow connection?` / CTA: `Switch to source editor`
3. . If someone opts to "Switch to source editor", that selection **should NOT impact** their preferred editor.
=== Mockup
{F37805533}
=== Open questions
- [x] 1. After how much loading time will we show the prompt this task is introducing?
-- 2 seconds [i]
- [x] 2. If someone opts to {nav Switch to source editor} will that selection impact their preferred editor? //Read: the editing interface they see by default the next time they attempt to edit a page on mobile.//
-- To start, someone opting to {nav Switch to source editor} will NOT impact their preferred editor preference.
--- //Thinking: we assume people will encounter this prompt relatively infrequently and thus conceive of it as a one-off choice, rather than a choice that will stay with them over time. Although, we'll learn the extent to which this is true and whether this approach needs to be revised in T347437.//
- [x] 3. What copy will we use for the CTA that simultaneously:
-- 1) Communicates the more "lightweight" nature of the source editor
-- 2) Does NOT introduce any new jargon (read: leverages language used elsewhere throughout the interface)
-- 3) Does not cause people to perceive the interface as being less complex to use
=== Done
- [ ] Requirements implemented
---
i. This 2 second threshold was informed by [learning the media load time for mobile VE is ~1.6 seconds](https://nbviewer.org/urls/gitlab.wikimedia.org/mneisler/mobile-ve-as-default-ab-analysis-2023/-/raw/main/mobile_ve_ab_test_report_2023.ipynb#Load-time). We assume