Replaced foreground with brush.

crates/api/src/properties/styling/foreground.rs

crates/api/src/properties/styling/mod.rs

crates/api/src/properties/styling/tests/foreground.rs

crates/api/src/properties/styling/tests/mod.rs

crates/api/src/render_object/text.rs

crates/api/src/widget/widget_container.rs

crates/widgets/src/button.rs

crates/widgets/src/check_box.rs

crates/widgets/src/list_view.rs

crates/widgets/src/text_block.rs

crates/widgets/src/text_box.rs

crates/widgets/src/toggle_button.rs