This is a new section in the extra keys option that allows to enter
arbitrary strings which are then added to the keyboard.
A new string is needed for the title of the section, Android's icons and
strings are used as much as possible to avoid adding more strings.
Keys are stored in the preferences as a JSON array of strings.
The newer haptic feedback API that is used instead of the vibrator
service since ef03dfe doesn't work for everyone.
The new vibration option allow to choose both the newer API ("system")
and the older API ("strong", "medium", "light").
