chore(windows): cleanup documentation

* Add QR Code help
* Remove unused images and ancient conent

fix(ios): Responsive predictive toggles

Fix/linux/setup gschema

* Return 0
* Set executable bit

fix(developer): upgrade removes preferences 🍒

docs(ios): Updates offline help for new 13.0 content

Fixes a compile hint as a rider

The uninstall is supposed to remove HKCU settings for developer. However
a side-effect is that an upgrade (which msi treats as uninstall/
install internally) also removes HKCU settings. This is sad and it is
probably better overall to leave a dangling HKCU key after uninstall.

Fixes #2667.

fix(ios): Engine demo fix

[Linux] Fix tier used in debian watch files

Add comment to watch file and simplify regex

fix(common, linux): Misc keyboard processor fixes for Xenial

fix(developer): crash importing blank OSK

Determine tier from `TIER.md` or environment variable `${TIER}`.

Use sed to replace any previously set tier in the watch files.

Fixes sillsdev/keyman-issues#6231.
Fixes sillsdev/keyman-issues#6125.
Fixes sillsdev/keyman-issues#5914.
Fixes sillsdev/keyman-issues#5902.
Relates to #2656.

If you attempt to import a blank OSK into the touch layout editor,
nothing happens, but behind the scenes the state was corrupted, meaning
when you attempt to continue work at some point the app will crash.

fix(developer): crash in context help

Fixes sillsdev/keyman-issues#6207.
Fixes sillsdev/keyman-issues#5801.
Fixes sillsdev/keyman-issues#5742.
Fixes sillsdev/keyman-issues#6186.
Fixes sillsdev/keyman-issues#6124.
Fixes sillsdev/keyman-issues#5647.
Fixes sillsdev/keyman-issues#5726.
Fixes sillsdev/keyman-issues#6149.
Fixes sillsdev/keyman-issues#6228.
Fixes sillsdev/keyman-issues#6001.
Fixes sillsdev/keyman-issues#6148.
Fixes sillsdev/keyman-issues#6159.
Fixes sillsdev/keyman-issues#6171.

This fixes a crash when context help is unable to determine the
current context.