Not possible to create a nested checklist on iOS

### What
Although it's possible to view and use nested checklists that were created on desktop, it doesn't seem possible to actually create a new nested checklist.

The closest possible solution is dragging the cursor in front of the checklist circle and pressing space a few times, but that doesn't actually work when the note is previewed.

### Why
A user reached out, expecting to be able to create one based on the info here: https://simplenote.com/2019/02/06/a-better-way-to-keep-track-of-your-tasks-check/
It doesn't explicitly say you can _create_ one on iOS, but it's sort of implied. So I'm filing this as a bug because it seems like it may be an oversight, although I am not 100% sure

### How
This part I don't know - given the lack of a tab key on the iOS keyboard, it would need to work differently than how it does on desktop

No files, tests, or code entry points are named. First reproduce creating a nested checklist on iOS and compare it with a desktop-created checklist, then determine an iOS interaction that supports nesting without a tab key. Done means a newly created nested checklist previews and behaves correctly on iOS.

Written by the indexing model from the issue text.