Find a way to make it so that themes don't have to define a
value for every attribute of every widget.
Applications can handle default values/links internally.(UPDATE 2024-05-14: Defaults will be handled by definitions
which will exist externally from applications.) Then, themes
can be made to override these values.
If a theme being applied does not have data for a widget's
attribute, the attribute will be reset to its default value/link.