This is more general, and necessary if the custom theming is dynamically
generated.
Iced's builtin theme also uses `Box`ed `Fn`, or `Rc` where clone is
required, so this seems reasonable.
Only `Text` is left using `fn`, since it needs to be `Copy`. Hopefully
that can be changed in Iced at some point.
`::custom` methods are added to make these variants a little more
convenient to construct. This replaces a couple `From` implementations,
which are potentially problematic with a generic.
We'll need libcosmic to work on Windows and macOS if we want to use it
in the Keyboard Configurator.
`freedesktop-icons` doesn't seem to build on Windows, so only use it
on Unix systems. It does seem to build on macOS, so leave it as a
dependency there. A good solution for icon bundling on macOS/Windows will
need to be figured out at some point.
- Updated example to show behavior
- Created styles for Expander and ExpanderRow
- Simpler implementation of `ExpanderRow`
- Deleted `ExpanderData` and replaced it with `ExpanderRow`
- Every row can now have child rows.
- Ran cargo fmt.
- Deleted settings example
- Added expander to cosmic example
- Expander icons now render
ListBox partially implemented
