The new key switches to any installed "voice" input method.
If several input methods matches, no effort is made to choose.
Might misbehave with some input methods other than Google's on API < 28.
It is placed on the middle of the arrows on the bottom bar. It is
enabled by default and can be removed in the "Extra keys" option.
The key is not removed from the keyboard if no voice input method
exists.
