When no widget has focus, press the letter key to focus on the widget
assigned to that letter.
Example:
GitHub (d)
Press "d" to focus on the GitHub widget.
Widget titles can now be specified in the config file via a 'title' key.
Example:
wtf:
mods:
todo:
title: Tada
which can include emoji. No need to force everyone to look at my emoji,
now they can define their own.
Widgets can inform whether or not they should get tab focus.
Widgets that provide additional functionality should return true.
Widgets that have no extra capability should return false.
This allows the FocusTracker to only tab through and focus on widgets
for which it provides value.
